not dreadful, but i think philo stone is a must buy on galio, he needs gold to be effective and if you arent in a solo lane your carry is gonna be PISSED at you taking all the minions. frozen heart is very poor on galio also, late game the 500 mana is so beyond unnecesary, and note that galio is best as a very tanky support, so you should be looking to build aegis of the legion and most likely another aura (depending on what your team needs) i also dont agree with the mana or AP runes. i also think thornmail isnt always the best build on a tank, as its just gonna put the AD carrys off attacking you. i also find health pots more effective than mana pots if you start with a mekki.

well i find frozen heart to be useful against players like xin,yi, or any fast attacking players.its just an alternative item but i try and build galio as a heavy magic resist character than a heavy armor character. frozen heart and thorn mail are just his optional items when facing a heavy AD team.

Frozen Heart is bad on Galio. Change it. Change it. Every item should work with the character completely. Or be so worth it that missing out on a certain stat is still outweighed by other synergistic traits, I.E. Trinity Force on Renekton. But the part of this item( Frozen Heart) that makes it a good item(slowing down DPSs) plays against your ult. What should be the best part of this item works against you; not good.

yeah that about covers it lol. But you got a firm grip of his mechs so keep on trucking and your guides will become better.

thanks for the comment and tellign me what im missing i will try my best for my next guide.

This build reminds me of how I used to play Galio :P I find a few problems but I wont downvote because I can tell you put alot of efort into this Build and you do know what your doing. You just need some "Icing on the cake" kinda stuff.
You have over 300 Armor. Now against a heavy AD team that is great for a tank, but for Galio to have over 300 armor and only 200ish magic resist isnt the best because you arnt a threat. "Oh Hey LOOK, Theyre is a squishie Ashe beside that tank with 300 Armor. IL GO FIGHT THE TANK!" doesent usually work... people arnt that dumb *Well some are*. You need to be a threat, you need to be the guy who can survive in the teamfight WHILE still doing some damage. Normaly for me my only armor items *against an average team* are frozen heart and aegis of legion. Its normaly all you need. But that is very situational items.

About the skill sequence, you get up your Q then your E. I used to always do that :P Ahhh, farming a whole lane INSTANTLY!... but then I learned your E sucks. Look at the damage output at level 5 vs your Q
Q=300+75% of AP
E=240+50% of AP
with 150 AP
Q=412.5 && E=305, Thats a pretty big difference.
Because your E isnt the best harrasing tool, I look at look at your W. at level 5 it gives you/your allie 90 armor and magic resist + heals you aton. I now get it up before my E, its way more useful and saves livse *yours and allies*
*But yes, I do get up my E at level 3, but for the speed boost*

Also you getting clarity is what I used to get, and its not a bad spell for him at all, but your early game is the only time clarity is even useful. So here is what I do.
Early Game I get Philophosers stone and then Chalice of harmony. Now you have 2 mana regen items, but one is a 5gold per 10 item. So after 23 minutes *so 25 minutes into the game* it pays for itself. i usually sell it at about 35 *so I make a big profit* and it gives you the much needed mana sustainability +some health regen. Now instead of Clarity since its not needed, I get teleport. A) It is benefitial at every stage of the game and B) When you get the money for Philophosers you can go back, buy it *to maximize its money early* and then tele back and not miss any xp :P

Im not saying this build is wrong at all :P I loved this way to play galio and won aton of matches :P its just those little sprinkles its missing *and cool graphics like kinda stuff :P*
Non the less, good job :)