I would suggest you both of Brand Name and site functionality as branding is so important these days due to search engines as for instance when u search gambling is faster to get "gambling.com" site rather than other non named such.
Same thing for functionality as the more you have the more appreciation and enthusiasm some new gambler will have to join your gambling site.
Usually, casino owners will think of using the word "gambling" in front or behind other keywords so that search engines quickly index them.
They use long-tail keywords to not be too competitive with other casinos and get a good position on search engines.
But if they continue to use short-tail keywords, it doesn't mean they can easily compete with other casino websites, especially with casinos operating for a long time and already have a good reputation.
Therefore, choosing the name of a website is very important and usually, this requires research to find the right name.