The problem is that you cannot conduct a full study of the legality of the casino business - they are mostly registered in offshore companies and you can assess the legality of their activities only by the comments of their users (are there any problems or not). But even user reviews cannot be trusted as they can be fake.
Start checking the validity of their gambling license first. At least have a valid license first. If there's none, check the ratings or feedback as you suggested, like in trustpilot. Since a lot of reviews are not authentic, you can check it for yourself. Send small amount of money and test the site. You will know how they treat the players if even small time players are not having any issues with them. An endorser should check the services for himself first and not just blindly promoting them.
Yes, these are reasonable recommendations and personally I do it easier - I only deal with the top of the industry who have been on the market for a long time and are beyond suspicion. But bloggers usually receive proposals from new projects and there the "legend" can be anything, for example: "the license is in the process of registration"
