Basically what I'm looking for is a credit type of system. Users can buy credits through PayPal, and those credits stick to their account. From there, users will be able to bet on games through Xbox Live, PSN, and PC with other users, and bet on the outcome of these matches. The credits are then awarded to the wining user, minus a 10% service fee.
In order to decide who the winner is, we need a reporting system. Players would both input scores, and if there aren't any discrepancies between the two, the player who won gets the credits. If there is a discrepancy, the match would be flagged for Admin review.
My website uses an e107 content management system, I'm not sure if that will help at all.