Great experience is an individual thing. You have to visit casinos and check their user interface and the functionalities. If you like the time you spend there and find it user friendly, then be assured that you have found a casino site that offers great experiences.
Promotion is also an individual thing but be careful with it, you must check the terms of promotions before you get too excited because many times there are very beautiful offers shown but behind the scenes, you need to wager too many times. But sometimes you'll find great promotions with great terms.

Focus on trust, gamble on casinos that are active on this forum and take trust seriously. This way, if something happens, you'll be sure that with the help of the community, your problem will be solved.
You'll quickly verify the trust of casino by checking the profiles of their representatives on this forum. The greener the trust, the better.