This is very simple, what are you looking for?
If you are looking for Canadian Casinos, check this site: https://candacasinos.com/ it really depends on what you are looking for, there are several online casinos that you can start promotion. You just need to know your niche and then to make sure that you have good and strong affiliate sites that reccomend the casinos and then you are all set. At Best Casino affilaites, they have also very strong brans, I personally work with most of them.
Check this out: https://casino-affiliates.net/