Cut out the middle man and get your own advertising instead. Adsense has one of the best payout rates in the industry, but you have to remember that Google is merely the middle man for every $1 they're paying out they would have to at least be making $5 - $10 more so they're always ahead.

With stats like that there isn't a reason you can't go out and solicit advertising yourself from gaming companies, stores and publishers and show ads yourself without using a third party advertising network. That is probably one of the most obvious pieces of advice I can give you at this point, but if I think of anything else I'll let you know.