Gragas is one of my favourite characters. He is one of the few characters that I immediately built my own way. (I usually check MOBA for a good build) I found that playing him with my own build I was winning quite often. I was able to survive alot of the teams damage and bring to the table my own significant damage. Not to mention the gold items plus Gragas' ability to clear entire minions waves in 2 seconds made for large gold pools every game. Every return I would have enough gold for my next item. Anyway I'm rambling...

Well I can't think of any way to fill up as much space with information as other builds do... Gragas isn't to hard really. Against a melee champ throw barrels on yourself or where you are going because if they want you dead, they have to go to it. Against a range AD champ, stay far away, your barrels can go further than their auto attacks. Harass them until you can see the kill coming and immeidately close the gap, your belly flop hits much harder than they expect and the slow will make them panic, any range champ stuck in close range is scared. Save your barrel for after the belly flop as the slow makes it a lot easier to land.

Your ult synergizes very well with your q, popping your q right as you land an enemy with your ult results in either an unexpected death or a terrified, overextended enemy trying to escapes the fat, ginger drunkard hobbling after them. Watching a Veigar go from full to nothing in 2 seconds flat always gets multiples "LOL"s in chat and makes you feel good man. Do it.

It has an active, use it.

I'm not really motivated to put to much detail in as I don't really expect anyone to see it. But if you do and would like more detail please tell me as I would definately put in more effort if I know it's helping someone.