I suggest modelling the odds after a real world casino. Have each player roll based on their Wisdom. Have each player declare their "stake" at the beginning of the night. You can RP each game if you want, but just have them roll to determine their winnings at the end of the night.
d20 + Wis Mod =
1-10: Lose entire stake.
11-14: Lose 50% of stake.
15: Lose 25% of stake.
16: Lose 10% of stake.
17: Break even (keep entire stake).
18: Keep stake and win 10% of stake.
19: Keep stake and win 25% of stake.
20: Keep stake and win 50% of stake.
21: Keep stake and win 75% of stake.
22: Keep stake and win 100% of stake.
23-25: Keep stake and win 200% of stake.
26-30: Keep stake and win 500% of stake.
31+: Keep stake and win 1000% of stake.
Honestly, that's about your odds at a real-life casino. I should know, I see it every day.
-TRRW
Edit: VVV What he said. VVV