You could have card games, shell games, dice, a form of slot machine as well as other games of chance.Prizes could be any thing from gold to items found in game depending on what you wager. Since with pretty much any game of chance the odds are in the house's favor it'd be a good gold sink and would also bring in more donations with people buying fsp to either turn into gold or if some games of chance took fsp to play.
Just a little idea. I used to code a long ago for a game and we constantly looked ideas for gold sinks as well as ways to reduce item count to relieve stress on the server and gambling seemed to work the best.



