People always come to me in games when i play AP gragas and say..."hey wtf you buildin AP for gragas is a tank noob" and i respond to them by getting a double kill in top solo lane with my AP gragas build. I find him a much more suitable AP burst champ than some easily avoided non-threatening tank. His ulty scales wonderfully with his AP which is fabulous for team fights and seperating the enemy team not just pushing them around with little damage as a tank gragas does but mess them up with a quarter of there HP gone after ulting

My skill order is Focus on Barrel Roll and Body slam while maxing Drunken Rage last. I start off with doing a barrel roll and secondly a drunken rage for lane sustainability. After that i get another Barrel roll to get some better damage on it, i follow up with a body slam getting it up to lvl 2. I dont get anymore body slams after that until i max out barrel roll. Then max out Body slam, then obviously Drunken Rage. :D and kill stuff with your new found super coolness.

Pros-
Great Burst
Fabulous CC with his ult
pretty tanky for a caster
Can set up great ganks with his ult
Amazing solo top champ as well as mid
Cons-
If missed barrel, you are ****ed
Lots of skillshots so as usual if you missed you can get screwed
hes a burst AP champ, so if you dont kill the person you can only melee for a while

I start by getting a dorans ring in start game for survivability as well as some damage. on first back you should be able to get boots of speed, blasting wand and a ward + health pot. On third back you should be able to get the Mana and Health Crystals or if your doing good the catalyst. after catalyst i pick up sorc boots for some needed movespeed and Mpen, later grab a Needlessly large Rod and eventually a rabadons.....after rabadons i finish my rod of ages......then its really situational after that. If you feel too squishy get some defensive items but if your still a wrecking ball burster than just keep steady with the AP items

As for my Runes, they're weird but trust me they work. Anyway i get Magic Pen Reds Magic Resistance Yellows because i always feel that i need my caster to be more resistance in laning phase.....and Clarity Blues because with Drunken Rage giving you mana as well you can stay in lane for evaz MUAHUAHUAHAHAUHH!.....anyway thats my rune page