I go by 9/0/21. I go 9 in offense so that my ability cooldowns are reduced and so that i may help ot my abilities with ap boosts. I go 21 in utility so that my summoner spells have a less cooldown and to help me with movement speed.

For my runes, I have 9 Grater Mark of Insight so that I may have magic pen. I then have 9 Greater Seal of Force so I can have a small AP boost. I also go 9 on Greater Glyph of focus so I can have my champion's ability cooldowns reduced. I have 3 Greater Quintessence of Force to help me with and AP boost for late game.

For my items, I start off with a Dorian's Ring which help me out in early game with an AP boost and health boost.Next I go for the Sorcerer's Shoes boots to help me chase, and run away from enemy champions. I then go for the catalyst the protecter which is part of the rod of ages.After I buy the Catalyst, I don't go shop until I have enough to buy Rod of Ages. I then then buy a blasting wand to help me with AP. After the blasting wand, it is helpful you buy the Giant's Belt. After, i don't go shop until I have enough to finish Rylai's Crystal Sceptor. This helps me with health and AP. After that item is completely paid off, I buy a Needlessly Large Rod which is a part of the deathcap. I buy the deathcap and then go for another Large Rod to buy Zhonya's hourglass. This item build helps Gragas with plenty of AP to do damage and plenty of health to stay in battle. After those 5 items arebought, I go for Guardian Angel to help me finish off low healthed champs in case I couldn't kill them before. P.S sell the ring when not needed anymore. To make room for the other items.

I get clarity so that if I am low on mana during a battle, I can restore while helping teammates with their mana. I also have teleport to get close to teamfights and to defend my turrets.

This build helps Gragas destroy squishy enemy champions and helps him stay in battle with all of his health. This build should help your teammates out and should be able to grant you some kills.

Use bodyslam to slam into enemies and to run away. Using bodyslam to slow and enemy and your q move to place the barrel directly in front of them can get you kills and harass enemy champs. Using your r can help you run away by blowing champs away from you or help you get kills by bringing champs close to you. When minions are all in a bunch, it helps to trow in your q barrel to clar them out, it should eb easy since you have alot of AP (: