Why ask for an initial number if it has to be $100, why not just say "Hit enter to bet $100"?

As for making this better, the only way from here is to throw away all this code (maybe you could keep the opening print statements) and write it properly. If you don't understand my original suggestion to use arrays read up on arrays and ask sensible questions about what you don't understand and we'll explain it to you.

If this was homework I'd set, I'm sorry but you wouldn't even get a bare pass mark.