My top affiliate programs are Vegas Affiliates (Microgaming), Mainstreet(RTG).
Also I can recommend WagerShare, CasinoCoins, FortuneAffiliates, ReferBack, GoldenStarNetwork ant others which I can’t remember now but promote them.
And I also want to add that all CAP certified affiliate programs are very good to start promoting them. All managers are friendly and always ready to help you.