One of the consistent problems I’ve noticed is that players always have too much of one resource or another (way too much, usually). In that case, the dwarves could offer to give rewards in a different resource than what you ante with - at a disadvantage, of course. Maybe a 3:2 ratio?
Mathematically, you’re always going to lose over the long term against the dwarves, so that’ll cut down nicely on what you can get back out of them, and since they allow you to gamble as much as you want, players can eliminate a lot of overstocked resources in ten seconds.
Also, that’d give people an incentive to use the dwarves, because I’ve never heard anyone care in the least about those things.