How about if you were given the ability to bet on everyone in the tournament, and when the tournament finishes and you win then you get your investment returned as well as a portion of the coins that people bet on the losers (depending on how big the bet was)
That is the general idea of gambling on games/tournaments. Fizzer will probably apply a 20% to you winnings, to make some coins of this gambling as well...
How about having the ability to coinbid for prizes, such as more coins or a membership, or even a pack!
Should I read this as an auction? "Selling 1 yearly membership, bidding starts at 10 coins!"