This guide is to show the full potential of Galio in Aram.

He has a full team taunt and massive pokes, making him ideal for this mode.

9-21 still gives enough damage to feel useful.

I didnt pick Second Wind because you will probably never fall under 25% Health and even if the 10% wont help much.

You have a snare and a stun making Oppression a great tool.

Double Edged Sword isnt a great choice since it counters your Damage Reduction and you are a tank.

And of course Legendary Guardian. 5 Champs around -> 20 Armor, 10 Magic Resist for free

Armor
Magic Penetration
Ability power per level
Ability Power

Your tankiness comes from items

Flash for the Flash Ulti, there is no other use for it.
You will finally be able to spend some money and need the Flash way more to engage with your taunt, if you think you are about to die do not use Flash to try and escape.

That is what Barrier is for.
If you really miscalculated and took a lot of burst, use it.

With the Items for Galio you are looking for
Magic Resist, Ability Power, Health, Armor and Cooldown Reduction

The Core items
Mercurial Boots - Tenacity + MR
Spirit Visage - MR + CD + HP + Increased Healing
Abyssal - MR + Ability Power + Reduced MR for enemies
Unholy Grahle - MR + CD + Ability Power + Mana Regen

If an Adc starts becoming a problem try to focus him at first with your Q E combo.
If you then start taking serious damage get a Chain Mail, there is no need to get Randuins or Thornmail yet.

After your core go looking for what you are missing against the enemy composition.

3 ADC on their team might mean a Thormail.
1 Fed ADC migth mean Randuins so you get the bonus HP
5 AP might mean you get an Aegis for the team

Try to see what might be best in the current situation

Max Q first
The slow helps chasing and does nice damage

Level E if you can and W if you must
In the end it's about the enemy teams playstyle.
W gives a huge amount of Healing for you and Protection for your mate,
while E gives more damage and Chasing capability.
So if they are engage-happy level your W and you will keep an additional damage source safe from burst damage.
Your Ult is going to do the rest to get the focus on you (#FlashUlt)

Take what you can get.
The others will take most of the kills so you need to get your core somehow.
After the first or second death you should be able to 1-hit-Q the caster minions.

I didnt mention his passive yet? Oh my.

50% MR --> Ability Power Bonus

Yeah, you build offense with defense!