Ah, gambling! The bane of all DMs everywhere. (OK, it's not that bad, but we've all met players who are way too happy to hang around town gambling to earn gold rather than adventuring...)
Here are two subsystems for gambling:
I) Winners and Losers (stolen from Savage Worlds)
1. Decide upon a stake (say, 5 silver pieces)
2. Every gambler makes a check
3. Subtract the lowest result from the highest result. The gambler with the lowest result pays the difference x the stake, to the gambler with the highest result.
4. Repeat the above steps for the gambler with the 2nd lowest result and the gambler with 2nd highest result. If there's an odd number of gamblers, the guy in the middle breaks even.
II) Winner Takes All (stolen from Star Wars Revised Core Rules)
Same as above, except in step 4, each gambler compares their result to the guy with the highest result and pays him difference x stake.
These systems can be resolved in a single check per participant (although there is a bit of arithmetic involved after making the check), and it doesn't matter what skill or ability you use. You could even have different participants make different sorts of checks (letting everyone use their best skill from Campbell's list, for example).
-- 77IM