The accuracy of your airsoft gun has alot to do with the BBs you are using. You only want to use high quality airsoft BBs with your guns. Otherwise it will damage your gun and/or greatly decrease your performance & accuracy. Lucky for you though, \we do not carry anything that we don't personally use and recommend. You want to steer clear of department / big box store brand BBs because they can and will damage your gun, along with voiding your warranty.
In general, the heavier the BB you use, the more accurate it's going to be. The only down side to the heavier BBs is they will get to the target a little slower then a lighter BB, and they cost a little more money. If you are playing indoors, there is no need to use anything heavier then a .20 or a .25. But if you are playing outdoors you really want to use as heavy as you can afford. Usually topping out with a .32 if it is a semi or full-auto gun. If you are using a bolt action rifle you are going to want to use the absolute heaviest you can find that is above .32.
Again these are all just generalizations, any 6mm BB will work with your gun. It's just about personal preference and making the right choice for the outcome you are looking for.