Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This is the Galio Build Ive been using (though I haven't been able to test out all of these runes). The thing I've noticed is that people only get items with magic resist. While this is helpful, it makes you miss out on some amazing tank items. The chalice is there to let me constantly spam spells, maintaining lane control and letting me harass my opponents. The mercury treads are self explanatory, extra magic resist plus decreased cc effects, yes please! The banshee's veil is for serious anti-caster, giving health, mana, crazy magic resist and an awesome effect. After banshee's veil, casters no longer are the issue, so I work towards the omen. Armor + Health + Health Regen + Cooldown Reduction (very helpful for getting your ulti off more) + Slow, this is my favorite tank item. Guardian Angel is generally your last item, and is self explanatory. The thornmail is there in case the game goes on for awhile or if you are fed (or both) and makes it really hard to kill you and makes your ultimate that much more deadly.