You can only learn a little from the mistakes of others but until you experience it yourself you will never understand the reality. When you use different casino sites you will know from your own satisfaction which casino site is best for you. And when you personally keep making various mistakes, you will gain a lot of knowledge from them which will help your conscience to avoid them later. no person can ever suggest you which casino site is the best. Because only you can understand better which one will be best for you according to your needs.
It's true nobody can tell him which casino platform is the best one where he can play, because each gambler has their own preferences and opinions regards what is the best available casino. But we can recommend a list of suggestions containing many alternatives of reputable and popular betting sites, so he can choose his favorite one based on this trusted list, without having to risk himself on unknown or shady casinos which didn't prove to be solid yet.
By list I include the casinos positively reviewed on this forum. So a good first step to be taken would be to start looking for the reputable casinos promoted at bitcointalk, so he can try them until finding which one best matches his personal preferences. There are also reviews websites across the internet, but I think this forum is the best spot to look for alternatives, since feedbacks here are shared in real time and in a more decentralized way.