^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. So it is expected that you will receive a small amount because it is rare that there is someone who gambles in a big time, not unless, your friend who signed up under your referral is a billionaire.
The referral fee or reward you will get differ from one casino to the other. Besides, some casinos will pay you on each deposit your referral make while others will pay based on how much the referrals lose. You have to read the referral program terms to see if it's worth the hassle before signing up.
If you are a streamer or an i fluencer then better check if the casino has an affiliate program or contact directly the owner and see if you can make a private deal with him.