As far a bb's go, I can tell you to definitely stay away from Madbull and Javelin .20 biodegradable bb's. It has not been just one bad experience with them, I've used 3 bags and many different guns, and they always acted the same. Just an FYI, Javelin and Madbull .20 biodegradables are the same thing.
Don't get "Matrix" bb's of any kind, they suck.
The best brand I have used was G&G, but Airsoft Elite, Madbull, TSD, and Excel all make excellent non-bios as well.
As far a bio bb's go, I would say that my best experiences have been with TSD.