Rizk seems good from what I can see, you level up and get two wheels to spin. Usually just free spins. VS and their weekend booster is pretty good, but their rtps are super dodgy. Dream Vegas and Casimba both have loyalty programmes but I am not a huge fan of their reverse withdrawal functions.
888 have also been in touch about deposit bonuses quite frequent.
Cheers, i only really play at VS, love everything about the place apart from that damn rtp% on play n go and a few others. will check out dream vegas tho, am sure thats where stop and step plays