^I don't know in general if a gambling casino industry will give the same percentage of referral from the revenue they will get, as I have known, it was ranging 5% to 10% of the revenue they received.
I have checked different casinos' affiliate/referral system, and they obviously have different reward rates, some are fixed, some are increasing by limited time say monthly when you invite more and etc.
And yeah, looking or having a regular referred gambler/user is not easy even having at least 1 to signup your link is not easy as well how much more for big time gambler.