So you basically want to cheat the user. Slot games are inherently random , yes, you set a possibility of winning but that's it..you don't decide if the user wins or loses. The best way is to generate a random combination and then calculate the wining on that (2 of a kind, 3, royal flush).

  If you want to do something like: if the user has less than 1000 $ ..let him win a bit more than usual.. lower the number of permutations.

Example:

User has 2000$...rolls once ..he has 5 x 5 x 5 slots possible if the user drops under 1000$ then he has 3 x 3 x 3 slots ( this increases the chance of winning a lot , but the animation looks the same so the user doesn't realize what's happening)

So you basically want to cheat the user. Slot games are inherently random. Yes, you set a possibility of winning, but that's it. You don't decide if the user wins or loses.

The best way is to generate a random combination, then calculate the winning on that (2 of a kind, 3, royal flush). If you want to let low-earning users win a bit more than usual, just lower the number of permutations.

An example:

User has 2000$ and rolls once: He is given 5 x 5 x 5 slots. However, if the user drops under 1000$, he's given 3 x 3 x 3 slots. (This dramatically increases the chances of winning, but the animation looks the same, so the user doesn't realize what's happening.)