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Galio Build Guide by TheMockingSnowman

Middle "Time to Make an Impact!" - Basics to Galio Mid

Middle "Time to Make an Impact!" - Basics to Galio Mid

Updated on July 8, 2021
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League of Legends Build Guide Author TheMockingSnowman Build Guide By TheMockingSnowman 13 2 33,956 Views 7 Comments
13 2 33,956 Views 7 Comments League of Legends Build Guide Author TheMockingSnowman Galio Build Guide By TheMockingSnowman Updated on July 8, 2021
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Runes: General/Tank

1 2 3 4
Resolve
Aftershock
Shield Bash
Bone Plating
Overgrowth

Sorcery
Nimbus Cloak
Transcendence
Bonus:

+9 Adaptive (5.4 AD or 9 AP)
+9 Adaptive (5.4 AD or 9 AP)
+8 Magic Resist

Spells:

1 2 3 4
General/Roaming
LoL Summoner Spell: Flash

Flash

LoL Summoner Spell: Teleport

Teleport

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Middle Lane
Ranked #17 in
Middle Lane
Win 51%
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Middle Lane Ranked #17 in
Middle Lane
Win 51%
More Galio Runes
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Threats & Synergies

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Champion Build Guide

"Time to Make an Impact!" - Basics to Galio Mid

By TheMockingSnowman

INTRODUCTION

Hello everyone and welcome to my Galio Mid Guide. I had main Galio for a while ever since I started playing League a few months before the end of season 10 with around 230K+ Mastery Points as of early 2021.

I want to provide my knowledge to anyone who are interested in picking up an anti-magic colossus but since I only play normal and 230K+ Mastery Points is really not that special, I fact-checked the information provided in this guide the best I can, using Internet, have it fact-checked by my high-elo friends, and such to do so.

I may not be qualified to make this guide but I do hope this guide helps anyone who wants to play the symbol of Demacia even by only a bit.
My only credibility (as of March 26, 2021)
"Time to make an impact!"
"The guy that made me, he was pretty good right?"

STRENGTH

* e Easy to pick up.
* e Flexible with different builds.
* e A team player.
* e Surprising damage potential.
* e Solid in any phases of the game.

Due to his AOE spells and crowd control, Galio is a strong team player who can turn the tide of battle whether it is a 2v2 with your jungler or a major teamfight. For a champion whose sub-class commonly have low-damage output capability, he can do a lot of damage due to his strong AP scaling ( Shield of Durand's tankiness scale with AP). He is also consistent throughout the game for the most part.

WEAKNESS

* e Struggle against match-ups with AD.
* e Get caught easily if not careful.
* e Rely on team.
* e Long cooldown on all of his abilities.
* e Can get poked a lot if not careful.

Due to his weak defense toward physical damage, Galio would struggle against a AD champion. All of his abilities have a long cooldown, making him vulnerable against champion with strong sustain. Since his abilities have long cooldown and the likes of Dark Harvest leave him pretty squishy, he is team-reliant regardless of the builds. Despite having a lot of crowd control, he can struggle to escape though not impossible.
"Magic goes in, might comes out."
"Punching time!"

PASSIVE

Colossal Smash
After a while, your next auto-attack is enchanted, able to do mini AOE magic damage to nearby enemies. An efficient strong waveclear tool that can poke the enemy.
"Good thing I don't bleed."

SPELLS

Winds of War
Winds of War, along with Colossal Smash, are your main waveclearing and poking tool. The two arcs of Winds of War can also damage the enemies so use that to your advantage.
Shield of Durand
Shield of Durand is packed with passive magic shield, damage reduction, and AOE taunt and magic damage that can be charged for stronger effect. You can quick tap it for quick taunt and damage reduction (not really useful, however).
Justice Punch
Justice Punch is your main engage tool during the laning phase. The range of it can catch unexpected players. Using Justice Punch backward when close to your opponent, will attack and knock the enemy up faster. Due to how it work, it can be troublesome if you are using it to escape.
"Hi, everybody!"

ULTIMATE

Hero's Entrance
A dramatic and fun way to zoom toward your ally to save them. It can also be used to save yourself but be wary that it can be interrupted. The magic shield from Hero's Entrance can save your ally from the likes of Karthus's ult and Lux's ult.
"Squish."
"Squish."

ABILITY ORDERS

"Squish."
Galio likes to help out his teammates as much as he can, which is why you want to max out Winds of War first. The sooner you can waveclear faster, the more roaming opportunities you have. Since Shield of Durand has a lot of things cramped in it, it is a good ability to level up next.
"Squish."
Maxing W first can be very valuable though, you still want to put 2 or 3 points in Q first for efficient waveclearing. Due to the recent nerf to Shield of Durand, this ability order is not as efficient as before.
"Squish."
"Squish."

LEVEL 1

"Squish."
Level 1 Winds of War
You generally want to start with Winds of War as it allows you to waveclear and poke early.
"Squish."
Level 1 Shield of Durand
Starting with Shield of Durand is great for invading or counter invading due to the AOE taunt.
"Squish."
Level 1 Justice Punch
Effective against a favorable melee matchup although the effectiveness of it is dependent if you can land Justice Punch. I highly recommend Aftershock if planning to use level 1 Justice Punch.
"Hahaha! This never gets old."
"You're going to need some mending."
Your bread and butter combo during the laning phase. It does a good amount of damage to win trade for the most part and it is very mana-efficient, allowing you to have enough mana for waveclearing, poking, and other trade. You can use Shield of Durand at the end of the combo instead of Colossal Smash if you want to move away after a trade. Charge time on Shield of Durand varies depend on the situation.
Your standard all-in combo during the laning phase. Shield of Durand can be used at the end of the combo instead of Colossal Smash. It does ton of damage but take good amount of mana so use it wisely.
A good follow up to your ult or massive movement speed buff. Also a mix-up option. You can use Justice Punch backward as seen in the video but using it forward works fine.
Your reliable way to land as many taunts as possible. Ghost represents anything that temporarily gives you a huge increase in movement speed such as Hextech Rocketbelt and Nimbus Cloak. Predator is uses in the video as it is commonly uses on Galio.
Good for snipping people from a good distance but be sure to point at the enemy you want to target. This work with the Active of Hextech Rocketbelt but it is not as effective in term of range.
"It's punch o'clock!"
"I'm a big man, with big needs."
NOTE: If I were to be at a Diamond+ level, I would have a section for laning phase, teamfight, and such. However, I am not and to hopefully prevent misinforming you people reading this, I decided to provide some tips I think will be helpful.
"You know what's hard about fighting? Nothing! Come on, I'm made of stone."
*i Hit & Run Strategy: During the laning phase, you should keep a good distance between you and your opponent. You only move forward to last hit minions and then move back as soon as possible (not too far away so you still can get some XP). This way, you minimize the poke damage you received. If it is too risky to last hit minions with a passive, you can use Winds of War instead.
"Feel the breeze!"
*i Galio is not a duelist so you should focus on teamfights or skirmishes with your team such as a 2vs2 with your jungler. You only want to trade if you are confident you can get a kill or able to do it safely.
"I'm sorry, I just woke up. Were we fighting?"
*i You generally want to move away as soon as possible after doing your combo.
"Whoa, I didn't know I had a tail!"
*i If you're going to use ult to save someone, be sure that you can turn the tide of the battle because otherwise, you will end up wasting your ult and potentially feed the enemies instead.
"Who wants to get protected?"
*i During mid game and late game and you're the win condition for your team, you generally want to farm in the lane near the lane where most of your team are in. For example you farm in either bot or top lane if most of your team are farming in mid lane. Be sure that your ult, Teleport, and/or any other methods are up when you are farming.
"At last a change of scenery!"
*i If one of your squishes is your win condition and even if you're also the win condition, you should go with them to push your advantage unless you have your ult and/or TP ready.
"Get behind me, huddled masses!"
*i Items To Consider Before Getting Mythic:
"I fought a house once. I'm pretty sure I won."
"Let me do the heavy lifting."
Flash
Flash is the most versatile summoner spell as it allows you to make either offensive or defensive play especially since Galio usually have a hard time getting out of the fight or chasing someone. When combined with Nimbus Cloak, you can land that 5-man taunt from Shield of Durand much easier. Flash should always be selected.
"Squish."
Teleport
2 teleporting abilities is better than 1. Teleport gives you a lot of map control since it allows you to go back your lane faster or join in the fight if needed. I would recommend this summoner spell if you do not know which one to choose. If you're using Predator then Teleport is highly recommended to maximize your map presence.
"Squish."
Ignite
Ignite gives you kill pressure and also a means to reduce enemy's healing, make it good against favorable melee matchup such as Ekko, Fizz, and Sylas for example. It does fall off as the game goes on.
"Squish."
Ghost
The extra mobility from Ghost can help out in roaming and getting out of a sticky situation. You do lose out on what the other 2 summoner spells have to offer through, it is not a bad option especially if you are using Unsealed Spellbook.
"Squish."
Heal
Due to the debuff from Heal, it is better if either an ADC or support select it. With Unsealed Spellbook, you can afford to go with this summoner spell. It's definitely a lifesaver in jungle skirmishes.
"I haven't been to many places, so I might as well like this one."
"Take your shot!"

RESOLVE


KEYSTONE
"Step right up!"
Aftershock
Aftershock synergy with Galio's trade pattern and role in teamfight. With it, Galio has better scaling with any items that give resistance stats. The extra Magic Resist Aftershock provided, temporarily increase Shield of Durand's damage reduction and the damage of Colossal Smash. Unfortunately, it does not scale well in late game and it has no AP scaling. Even so, the offense and defense it provided along with being easy to use and being usable in any matchups, makes it the most reliable keystone for Galio.

1ST ROW RUNE
"Bring it."
Shield Bash
Shield Bash make your passive magic shield, not only more resilient against magic damage but also capable of taking a bit of physical damage. It also adds extra damage to your auto-attack when shielded.
"I. EAT. MAGIC!"
Demolish
While Galio is able to damage turrets effectively without it, Demolish is still helpful if you want to do more turret damage especially if you want to get a lot of golds early on. You only want to pick this if you're confident that you can win your lane without Shield Bash.

2ND ROW RUNE
"Well met, giant zapping man!"
Bone Plating
Good against burst matchup such as Akali or Fizz for example. Be careful since a smart opponent would poke you first or any other safe way to get rid of Bone Plating before fully committing to trade.
"I've got a high tolerance for magic. Takes a lot for me to feel it."
Second Wind
Second Wind provides HP regen after taking damage which is useful against poke-heavy matchup such as Neeko or Lux.
"To battle!"
Conditioning
Conditioning provides extra Armor and Magic Resist which improve the sturdiness of Aftershock. You do lose out on some survivability in early game but you can go with this mini rune if you think Bone Plating or Second Wind is not needed.

3RD ROW RUNE
"I might be made of stone, but that doesn't mean my heart is."
Overgrowth
With Galio's amazing waveclear, you should be able to get a good amount of health increase. Overgrowth is good on Galio as the bonus HP makes your passive magic shield stronger as well increasing the damage of Aftershock.
"Stone cold."
Unflinching
Good against CC-heavy teams especially if you want to buy Plated Steelcaps or other boots. It also provides slow-resist which helps reduce the self-slow debuff from Shield of Durand.
"I came to chew bubblegum and kick butt, and I'm all out of butt."
"Wanna go?"

DOMINATION


KEYSTONE
"Fight me, small warrior person!"
Predator
Predator provides high mobility, allowing you to roam efficiently early in the game and not have to rely on the likes of Nimbus Cloak and Hero's Entrance. It is also consistent throughout the game and you have a lot of build flexibility including using other trees as your Secondary. However, you do not have the extra defense Aftershock provided, making it risky to trade against your opponent. It also has a high skill cap but the high mobility it provides, makes it a worthwhile option for Galio. Remember to buy at least a Boots on your first back.
"Gotcha!"
Dark Harvest
Those that want to do tons of damage with Galio, should definitely pick this keystone. With Dark Harvest, his damage scales super fast. However, you lose the safeness of Aftershock. Furthermore, you're basically limited to building AP items and you have to kill a lot to maximize Dark Harvest's potential. Because of it, it has some skill floors. Despite the major problem it has, it is a solid keystone for Galio especially for those that want to do crazy damage.
"I'll take you all on!"
Electrocute
A solid substitute for Dark Harvest if you do not like the playstyle or against a trade-heavy matchup. Similar to Dark Harvest, you are basically a glass cannon and have to focus building only AP items. Since it has a 25-20 second cooldown and you proc it by doing your combo, it falls off a bit in late game due to the many teamfight situations during that time. Even so, Electrocute is far from being a bad keystone for Galio and a strong option on it's own right.

1ST ROW RUNE
"Not a fair fight."
Sudden Impact
Gives you extra Magic Penetration for a while after dashing, teleporting, or blinking (also after exit out of stealth but Galio isn't a stealthy type). Since Galio can activate it pretty easily, it is a very valuable mini rune for extra damage.
"Freedom punch!"
Cheap Shot
Galio has plenty of crowd control thus, he can activate Cheap Shot very easily. The extra true damages is not too shabby either.
"Punching time!"
Taste of Blood
Since you are squishier with Domination as a primary tree, Taste of Blood is useful for giving you some means of sustain in lane.

2ND ROW RUNE
"Let me do the heavy lifting."
Eyeball Collection
Getting up to 30 AP after slaying enough enemies is simply good. Since it is reliant on you getting kills and assists, it can be difficult to gain stack if you are behind.
"Didn't I fight you yesterday, or was that a different puny thing?"
Ghost Poro
Replacing the expired ward with a spooky yet cute Poro while giving you AP for each time it get spotted by the enemy. It is useful not just for getting stacks faster but also more uptime for your wards. It is not a beginner-friendly mini rune however.

3RD ROW RUNE
"I sleep, I wake, I break things"
Relentless Hunter
While it may seem as an underwhelming mini rune, having more mobility outside of combat is extremely valuable as it allows you to roam faster, get to your lane faster etc.
"So... what do you people do when you're not fighting?"
Ingenious Hunter
Cooldown reduction for Active items means more uptime for Hextech Rocketbelt, Zhonya's Hourglass, and the likes. It also reduces the cooldown of Predator.
"Hahahaha, did we win yet?"
Ultimate Hunter
Since Hero's Entrance have a long cooldown, Ultimate Hunter is useful for getting more uptime for Galio's ult. A solid option overall.
"Eh, never been much of a reader."
"A paginated collection of words!"

INSPIRATION


KEYSTONE
"A book! Oh, just need someone to turn the pages for me."
Unsealed Spellbook
A keystone for those that want more utility. Access to more summoner spells means more uptime for Nimbus Cloak plus Galio can make good use of the summoner spells available. However, it is very hard to use. One of the main reasons being you have to figure out the best summoner spell for the current situation which is easier said than done. Furthermore, you only want to swap the summoner spell that is on cooldown which can lead to awkward situations. It's still a pretty good keystone for Galio, despite the learning curve.

1ST ROW RUNE
"I don't know what this is. I bet it's great though!"
Perfect Timing
A valuable mini rune if you are planning to buy Zhonya's Hourglass pretty soon. You get a small discount on the item along with a Stopwatch but you cannot use it right from the get-go, however.
"This is perfect! I too am very old."
Magical Footwear
Magical Footwear gives you free boot after a while which saves you 300 golds. Since there are situations where it is better to get boot early, you only want to use this if boot is not needed early on.

2ND ROW RUNE
"Hmm... doesn't come with instructions."
Minion Dematerializer
This mini rune gives you 3 Minion Dematerializer which not only completely erase the minion of your choice but also have increased damage toward those types of minions. Able to waveclear even faster means more roaming opportunities.
"Haha! Tiny."
Biscuit Delivery
Giving you up to 3 biscuits for extra sustain in lane especially since you do not have Aftershock and the rest of the Resolve tree. I suggest using all of the biscuits whenever you can since the sell price is very low.

3RD ROW RUNE
"Squish."
Time Warp Tonic
You definitely want to pick this mini rune if you're buying Corrupting Potion as a starting item since you instantly restore 50% of HP and MP you normally recover. It's basically become non-existent later on, however.
"Go time!"
Cosmic Insight
While it no longer has cooldown reduction on abilities, it can be a useful mini rune especially if you're going to be using summoner spells and Active items a lot.
"Smashing power amplified!"
"Yes!"

SECONDARY & SHARDS


SORCERY
"Looks dangerous... let's fire it up!"
Nimbus Cloak
Nimbus Cloak is still a good option for Galio despite the numerous amount of Active items and other options that provided similar mobility. Since Nimbus Cloak gives you temporary movement speed when using summoner spells, you have a strong escape or gap-closing option right from the get-go. If you're using both Predator and items like Hextech Rocketbelt then, you don't have to use this mini rune.
"Hey, you. Don't mess with Demacia, I saw you thinking about it."
Transcendence
With the new change to Transcendence, it basically removes the long cooldown of Galio's abilities after meeting the condition. You also get up to 10 ability hastes with it.
"Rest in my ample shade."
Celerity
A solid option if you want a bit more movement speed. It also make things like Hextech Rocketbelt and Predator more effective in term of mobility.
"Which way's the fun?"
Absolute Focus
If you want more AP and you're confident that you could maintain the above 70% health condition then this mini rune is for you. Be mindful of Galio's kit lacks a way to restore health if you're thinking of picking this mini rune.
"To battle!"
Waterwalking
Waterwalking is a situational pick that provides a useful stat for faster roaming and advantage during objectives. You can pick this mini rune if you know you're going to be in the river a lot.
"Know of any battles? Just looking to get my wings dirty."
"Dang right, Demacia!"
SHARDS
You generally want to get double Adoptive forces for a bit more damage to waveclear faster and such. Furthermore, you get either Armor or Magic Resist shard depending on who you are facing against. You don't have to go with this setup if you prefer using other shards but be wary that Attack Speed shard doesn't benefit Galio much.
"So... what do you people do when you're not fighting?"
"Hehehe, I like buying person things."
NOTE: While Galio can build Mage items and Tank items, it is better to go AP items since he scales better with them. Even so, building Tank items on Galio is viable and there are some situations where it is better to go purely Tank. You can also build 1 or 2 Tank items if you prefer.
"Squish."
"Squish."
"Squish."

STARTING ITEMS & BOOTS

"Squish."
STARTING ITEMS
"Squish."
Doran's Ring
Doran's Ring has been a consistent starter item for Galio as it give anything he needs for the laning phase while being usable in any matchup.
"Squish."
Dark Seal
A good starter item if you're confident that you can snowball the game. You can get up to 65 AP for a mere cost of 350 golds which is crazy good plus you can upgrade it further. With the extra golds, you are also able to buy Refillable Potion or 3 Health Potion.
"Squish."
Corrupting Potion
Corrupting Potion is a solid starter item for Galio as it provides him sustain in lane. You do lose out on AP which make waveclearing a bit slower. You generally want buy this if you have the Time Warp Tonic rune but it can still work without it.
"Squish."
Doran's Shield
Good against matchup such as Lucian, Zoe, and the likes. It gives you a good amount of sustain and pairing it with Second Wind will help you recover from poke damage even better. However, you will be waveclearing a bit slower.

BOOTS
"Squish."
Sorcerer's Shoes
This boot is really good for the extra damage. The flat magic penetration it provided helped kill squishes easier. You generally want to go with this if you think Mercury's Treads or Plated Steelcaps are not needed.
"Squish."
Mercury's Treads
The inclusion of Tenacity, makes it an ideal boot for CC-heavy matchup. The boots have some value on Galio since some of his abilities scale with Magic Resist.
"Squish."
Plated Steelcaps
Very helpful against AD matchup especially since Galio have pretty weak defense against physical damage. The passive is ideal against auto-attack reliant champions such as Master Yi, Vayne, and Lucian.
"Squish."
Ionian Boots of Lucidity
Transcendence is enough to reduce the long cooldown of Galio's abilities but Ionian Boots of Lucidity is still a good option if you want more Ability Haste or you are not using Transcendence. It also provides cooldown reduction for your summoner's spells too.
"Might need to loosen that a few hundred notches."
"I know, I'll wear it as a ring!"

MYTHIC

"Squish."
MAGE
"Squish."
Hextech Rocketbelt
Hextech Rocketbelt is a ideal item for Galio as it provide anything he wanted. It gives good amount of Health and Ability Power while also provides some Ability Hastes and flat Magic Penetration. Furthermore, it provide more flat Magic Penetration through Mythic passive. To seal the deal, the Active give him much needed mobility for gap-closing, basically having Nimbus Cloak + Flash for every teamfights. Due to the recent nerf to the Active, it is not as effective as it was before but nevertheless Hextech Rocketbelt remains a strong Mythic for Galio.
"Squish."
Everfrost
Everfrost is solid Mythic for Galio. It provides Health and AP stats along with having a decent build path. The Active is a strong follow-up option to your combos since it can Root and Slow the enemies. You can argue that the Active is redundant on a champion with plenty of crowd control but the Active is definitely helpful against high mobility and aggressive teams. Mythic passive is very lackluster especially since other Mythic have a more valuable Mythic passive. The item also lack the way to let you engage effectively though, it is not much of a problem if you have teammates that can engage effectively or have Predator keystone.
"Squish."
Shurelya's Battlesong
Shurelya's Battlesong has been used on Galio a lot for a while due to the Active and low price. The Active provides a lot of movement speed for you and nearby allies, making it a great tool for engaging or disengaging plus the Mythic passive is not bad ever. With the changes to the item, he is rarely able to use the Motivate passive since he does not have a lot of things that can empower or protect his allies consistently. Along with the Active no longer gives damage buff for you and your allies, this Mythic is no longer an optimal item for Galio anymore. If you are planning to use this Mythic, beware that you will be more reliant on your team.
"Squish."
Night Harvester
Night Harvester is a great option for doing tons of damages. It provided efficient stats and the Passive is solid for repositioning and the extra damages. The Mythic passive is helpful to reduce the long cooldown of Galio's abilities. However, you are not able to engage efficiently since the movement speed only kicks in when you damage someone. If you use a Predator keystone, have teammates that can engage, or you do not mind not having the movement speed Active, you can definitely go with Night Harvester.

TANK
"Squish."
Turbo Chemtank
Turbo Chemtank is a great Tank Mythic for Galio. The Active provides a movement speed buff and a shockwave that slows enemies, making it a solid engage tool. Furthermore, it contains an Immolate passive, giving Galio another source of damages. With the price of 2800 golds, it is a very efficient item for those going Tank build on Galio.
"Squish."
Sunfire Aegis
Sunfire Aegis is a strong Mythic for any tank. The main reason being it allows you to do a good amount of damages while being pretty tanky. Unfortunately, it lacks an Active that gives massive movement speed increase. You should only pick Sunfire Aegis if your team has enough engage.
"Squish."
Frostfire Gauntlet
A decent Mythic but it is outclassed by other 2 tank Mythic. While the frost field Passive is solid, Galio doesn't need it since he has a good amount of crowd control. It can be useful against high-mobility teams and Mythic passive is pretty good on Galio.
"Make me stronger, purple zapping stick!"
"Punchy spikes!"

CORE ITEMS

"Squish."
MAGE
"Squish."
Zhonya's Hourglass
A common 2nd core item on Galio. This low-cost Legendary item provides a nice increase in AP along with some Armor which helps with Galio's vulnerability toward Attack damage. The main reason many players buy this item is because of the Active. The provided invincibility from the Active is very useful especially since you're usually a sitting duck after using all of your Abilities. The item can be bought as a situational item against an AD-heavy team if you prefer other Core items.
"Squish."
Banshee's Veil
Banshee's Veil is a very efficient item on Galio since he scales with both AP and MR. The spell shield passive is useful especially against CC-heavy teams although it can be taken down by a single poke. It can be bought as a situational item or even 3rd item as well.
"Squish."
Horizon Focus
Horizon Focus is a budget version of Rabadon's Deathcap, making it a strong 2nd core item if you prefer to do more damage. Galio gets a lot of benefit from the huge amount of AP this item provides plus it has a very efficient build path. The extra damage increase from the passive is pretty good and it can be activated easily since Galio have a lot of CC. I would not recommend buying this as a 2nd core item if you are using Aftershock since you would fall off far more.
"Squish."
Lich Bane
A strange choice but Lich Bane work decently on Galio. The Spellblade passive works well with Galio's combo and the passive movement speed is just simply good. However, other champions can make better use of this item and it does not have a lot of AP nor any other stats beside the 8% movement speed increase. Similar to Horizon Focus, I would not recommend buying this item when using Aftershock as Galio would fall off harder in late game.

TANK
"Squish."
Gargoyle Stoneplate
A really good tank item in general. It provides a lot of both Armor and Magic Resist and you get more as you take damage. As if that is not enough, you also have the Active that allows you to take tons of damage, making it really useful for teamfight. The main drawbacks with this item however is it's high price and mediocre build path. As an item inspired by the colossus himself, it is fitting that it is a good item on Galio (and any other Tanks, of course).
"Squish."
Dead Man's Plate
The provided Health, Armor, and mobility make it a solid core item for those going Tank build on Galio specifically if facing heavy-AD matchup. It also makes your auto-attack slow the enemy once you stack enough Momentum. However, it is better to buy another situational Armor item plus you do not want to have too much Armor due to how Armor stat works in the game.
"Squish."
Abyssal Mask
Abyssal Mask is great if you need the extra Magic Resist and a very efficient tank item on Galio overall. The passive is ideal on a champion with strong crowd control and especially for a teamfight situation.
"Can I exchange this for a size seven-thousand?"
"Hmm... it doesn't fit. Well, guess I'll just hold it."

SITUATIONAL ITEMS

"Squish."
MAGE
"Squish."
Void Staff
Void Staff has been a great anti-Magic Resist item and with the added component, Blighting Jewel, the build path is very efficient. Because of how gold-efficient it is, you can build it as a 3rd or 4th item even against squishes.
"Squish."
Morellonomicon
With a lot of healing around, Morellonomicon is an extremely valuable item for anti-healing. Since it is a gold-efficient item on Galio, you can buy it for the stats alone though you can get away with just buying Oblivion Orb and then finish it later.

TANK
"Squish."
Thornmail
A great tank item against a team with a lot of sustain while also providing a good amount of Health and Armor stats. Since Galio has plenty of crowd control, he can easily apply the 60% Grievous Wounds.
"Squish."
Randuin's Omen
Randuin's Omen is a beefy Armor item that is ideal against Critical damage user due to the Active and Passive.
"Squish."
Frozen Heart
Frozen Heart is great if you are facing a champion that uses a lot of Attack Speed. However, it lacks the Health stat and Galio does not really need Mana.
"Squish."
Force of Nature
A solid item for the extra Magic Resist and mobility. However, it is outclassed by Abyssal Mask since the Abyssal Mask have a much more suitable passive for Galio.
"Squish."
Anathema's Chains
Designed as a anti-split pushing and anti-carry item, Galio can take advantage of the passive especially the passive that reduces your chosen nemesis's Tenacity. The stats on the item is also efficient on Galio.
"I'll use it as a toothpick!"
"Armour, kinda makes you feel like you're made of stone."

OTHER ITEMS

"Squish."
MAGE
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Mejai's Soulstealer
An upgraded version of Dark Seal. It can stack up a lot of AP on top of providing Health and movement speed increase for such a low price for being a Legendary item. However, you lose more stack upon death so you should only get this item if you have at least 8-10 stack on Dark Seal and you are confident you're not going to die a lot.
"Squish."
Rabadon's Deathcap
It always has been a powerful item due to the absurd amount of AP it provides. Galio have a strong scaling with AP, making this item very valuable. Unfortunately, it is very expensive, making it more of a late-game item.
"Squish."
Cosmic Drive
With the new changes to Cosmic Drive, it became a well-rounded item as it provides Health, AP, and Ability Haste stats along with movement speed increase. Main issue with this item is finding the item slot for it since you most likely would buy an item that suits the situation you are in. It can be bought as a 2nd or 3rd core item if you prefer.
"Squish."
Demonic Embrace
This item seems good on paper since it provides a solid stats and he can easily get the maximum Armor and Magic Resist from the passive. However, Galio does not do consistent damage meaning he cannot use the passive efficiently compared to other champions. Even though Galio cannot use it consistently, the burn damage does percent max Health damage, making it a decent anti Health stacker item. It is definitely not a bad 3rd item on Galio either.

TANK
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Warmog's Armor
Warmog's Armor is a solid item as it provided a lot of Health increase along with Health regeneration. The extra Health makes your passive magic shield and the damage of Aftershock and Immolate Mythic much stronger. While it is possible to buy it as your 2nd item, it is better to buy it during late game since a couple of tank items are needed to utilize Warmog's Armor effectively.
"Squish."
Demonic Embrace
Surprisingly a decent 2nd core item if you're going Tank Galio. With the combination of Immolate Mythic and Demonic Embrace, you will deal a lot of burn damage. However, you fall off a lot harder especially if you are not constantly snowballing.
"My middle name is Justice. Galio Justice Justice."
That's all folk! I do hope you find this guide helpful in a meaningful way. Some information in this guide is from other sources and I want to give credits to them.
*i Huge thanks to my high-elo friends for coaching me. Some of the tips here are from them.

*i Thanks to my other friend for proofreading and suggestions.

*i Both ThaKinetic and Coach Curtis have good videos about Galio though some of it are outdated.

League of Legends Champions:

Teamfight Tactics Guide