In Star Trek: First Contact, Picard plainly says that there is no money in the future:
Picard: The economics of the future are somewhat different. You see, money doesn't exist in the twenty-fourth century.
Lily: No money! That means you don't get paid.
Picard: The acquisition of wealth is no longer the driving force in our lives. We work to better ourselves...and the rest of humanity.
Does that mean that there are no stakes to the poker games played by the officers on the Enterprise-D? Or were there alternative stakes that didn't involve money?