Welcome to to one of my favorite champion builds. I usually go for this build because it makes it very hard for you to be killed and their is the added bonus of you hitting extremely hard in levels 4-16. I hope you enjoy the guide.

The runes I choose are good for Galio because of his passive which converts magic reis. to Ability Power. All the magic resis really helps but you could also change the mark (Greater Mark of Warding), for Greater Mark of Insight. This will give you extra magic pen which will be more beneficial late game.

As far as Masteries go they are pretty strait forward, so I wont really go into detail about them except for the fact I didn't spec into Evasion. I don't spec into this because it can effect you ultimate if you are unlucky and reduce the damage it does.

I start out with Null-Magic Cloak because it makes Galio start out with 102 magic resis. which just about makes him indestructible against an Ability Power mid (unless they have Magic Pen. Runes). They health/mana pots are just for the laneing power they give you. I usually use the man pot after I use clarity. The Null-Magic Cloak also helps a lot because its part of the Mercury Treds. Next I go into a Guardian Angel because at this early stage of the game Galio's damage is hard to ignore which means sometimes he will be the focus in team fights. So the Guardian Angel is always their is a fail safe. The Aegis of the Legion is a very helpful item for you and your whole team because it makes your defense higher along with teammates around you. Next I get Abyssal Scepter because it gives you both Ability Power and Magic Resis. and it reduces the magic resist of enemy's around you. Next is Rabadon's Deathcap because Galio's damage starts to become week this far into the game and the Deathcap just helps it out a bit. The Banshees Veil is for of course it Unique Passive and for the Magic Resis., Health, and Mana.

For my skills I usually try to launch a Resolute Smite along with a Righteous Gust, at low levels this combination of abilities does massive amounts of damage if they both hit. You can also use Righteous Gust to get away if you get in trouble, just point it the direction you want to go and follow the path it leaves.I usually use Bulwark on the teammate that gets focused the most late game, it increases their armor/resis. and when ever they get hit you get healed for a small amount.

I choose flash because it a very helpful spell on Galio. First off its always a good escape, but the main reason i use Flash is because I can flash in on team fights if I'm late for them and use it. I can usually save a couple team mates like this. I choose Clarity because it helps a lot during the laneing phase of game, when you get low on mana just use it and you will be back to about 4/5 mana.