That's a tough one, it will be pretty hard to get decent
conversions for a site unrelated to poker/gaming I would think. Now maybe if you went the sports betting route that might be better. Seems more logical to me.
I would not be concerned with people copying you, even if they do you just need to put more work into it.
As far as being outspent, that can be an issue, but some of the best affiliates to not need a 5 figure budget to do well, and you don't either. Be original, that's something you cannot buy.