Hi, I'm aronzei and this is my first guide on mobafire with the champion Galio. I'm quite new to LoL but I've taken grasp to most of the champions and mechanics. Needless to say, this is still a work in progress founded on previous top guides I've already read here - and to those that made the guide, thank you. This guide aims to improve upon considering a certain aspect - role.
Particulars are discussed further in.

Common:
Ignite
Flash

Recommended*:
+ Cleanse
+ Clarity
+ Surge

* Arranged by usability with the top being the most

- Ignite is better off with your lane partner for him to get the kills.
- Clarity is good if your partner is quite mana hungry (with some for you to yay!) Quite ignored late game.
- Surge provides the additional omph for the kill. Cast ult then this.
- Cleanse is highly valued. Provides CC immunity for 3 seconds. +1 more if you get the upgrade. Ensures your ult that goes for 2 seconds.

Ah yes, the core of this build for the role of initiator. This is where I cancel most of the items that I believe can be replaced with more useful ones - theoretically though. I am yet to use Galio in PvP.

So let's put our first item on spotlight shall we?
Let's us answer "Why?" and "Why not?"
The tanky combination
+
Why? Both providing MR this two is your primary survival item. As an addition on RoA, it boost overall survivability by immense regeneration. Players have a tendency to focus on the one with the least hp and you can tread that red-zone without fear. The FoN is inherently well with itself but by adding visage improves the already good effects of FoN and the heal of Bulwark. This also prevents you from dying saving you from respawn time while using the Q E combo to effective runaway from all those chasers. Keeping alive is your best option so that when your team needs you, you will be there.

Mana

Why? Mana. Every casters problem. I know getting blue is good but what if your teammates need it more? It is better you DON'T get any red's or blue's because you are already self-sustaining. This item makes sure you have mana to cast atleast 1 spell in your arsenal even if your last cast depleted your pool. Upgrading it eventually provides CDR so that your ult becomes available faster for you to ensure your team wins a clash.

Fiddle-like


Why not? This item, although great overall boost on ALL aspects Galio needs, it is better off with your team's nuker. Although you are close enough to ensure that the enemy is reduced during the fight, your nuker must also be within the fray for it to be 100% effective. When you cast your ult and your nuker enters however, this item will shine.

TouchMeNot


Why not? Yes, a good item. But ask yourself, if your enemy knows you have a tm, will they attack you? Of course not. It's an anti-taunt. Just seeing you with it makes you the least of the priorities. I'd rather go Sunfire Cape. AD carries won't focus you until they've taken out your carry/ies and Sunfire Cape. However in a game where your team is not dominant. It's better to take this to make sure you take out a good chunk out of those AD carries. This item can fill in the slot for Banshee's veil if there is a scarcity of CC within the enemy team. Banshee only ensures that you can cast your ult for its entirety without anyone disrupting you.

I suggest going on the generic. However, I'd like to point out that the items Galio will be built upon is mostly tanky so adding tanky quints is not favorable. MR quints however add both offense and defense so it can be considered an entirely different case. In particular, health regen/boosting runes are not advisable.

I know most of the other guides already covers what most of I could type so I will leave it at that. (eg. Harassing, Creeping, etc.)

Bottomline:
This is an in depth item guide for Galio as the team's tanky initiator. It adds CDR from masteries and items not previously considered in other guides augmenting his ulti that takes a whopping 130 seconds without any reduction.
(Currently 8.1 + 4 + 15 + 10 = 37.1% without blue)

And of course, teamplay! Communication is the key.
Galio is a teamfighter. Use that to your team's advantage.
You can't perfect it at first try but with practice and prediciton, you can atleast provide what you partner needs at key moments.

Lastly, thank you for reading.

Everything is still prior to change.