Prinnceszs said pretty much everything you'll need to improve your guide.
Sometimes I get Wit's End to bring towers down faster.

Consider adding more optional items, viable summoner spells, runes, laning, your role in team battles, tips and tricks etc. Don't forget to use colors, bold, underline to point out important things.

Going to keep watch on the guide and how it turns out. :)

Also +rep for Prinnceszs, he knows his $#!7.

Frozen heart... and sorcerer's shoes. BIG MISTAKES ON GALIO. Sorry if you were trying something different, but sometimes different doesn't work.

As an experienced Galio player, I'm sorry to inform you that your guide contains a number of critical shortcomings. However, you demonstrate you clearly have some skill with the champ and some knowledge of his gameplay, which is commendable. It just seems like you're not utilizing his skill set to the fullest. For example, why would you take dodge masteries? His ult scales off of how many times he is it, which is why dodge masteries and items like frozen heart (which slow down attack speed) make his ult less powerful.

Furthermore, you seem to forget sometimes that Galio is a tank. Magic pen quints over health quints make for a squishy early game. And sorc's shoes do not provide the beautiful utility of Merc's treads - which also provide you AP due to your passive! As a final note, given you are the tank and will hopefully die more than your carries because you will absorb damage and sacrifice yourself for the good of your team, you should always take Good Hands over Perseverence. All just things to consider moving forward and improving your guide. Maybe also include a section on Galio and team play? He's extremely dependent on his team, even more so than other champs sometimes. He provides great support, utility and damage and can tank like nobody's business, but he's not a solo queue champ - you need teamwork and people you can rely on to maximize his full potential.

All the best moving forward,
Prinnceszs

FINISH IT ******* IT!!!