Galio is great... as long as you dont use his E for laning, and farm carefully, there is no mage that will beat you in mid, im serius, i have done it. save that E for ganks and teamfights, dont waste it to poke, cause its weak at all lvl under 4, especially considering it has a high mana cost.
when going damage, max his Q the W
When stalling the lane and waiting for jg, get 2 on W, then 1 on Q, repeat untill W is max, then finish Q.
only person that i have problems with when i use galio, is brand, cause his abilities deal max health and the passive burns off the W stack fast (the W heals you less the more times you get hit, so when Brands passive hits you 3 times from 1 ability, the next ability wont heal you like you hoped)
Other than that... BRING ON THE MAGES BITCHES!!!!!