Assuming you gamble on a mid to high-rated gambling website and you won big but they refuse to pay up, what and what are the legal way to make sure that the platform pays up your money?
We as small customers cannot take much action if this kind of fraud occurs. But I will complain on different sites like ANN threat casino chatting site etc section. And I will tell all the members about my fraud.To them I will reflect the integrity of the entire incident. If every customer is aware then slowly all those casino sites will be destroyed.
If this happens to anyone, the needful to be done is to make complains to any reputable cryptocurrency platform, this should be done with a clear evidence to show how real it is. Making awareness is just the best because it has a final result.
reputable cryptocurrency forum? in which? Bitcointalk?

the best thing to do is to check if they have representative in this forum because if none? then for whom you will complain here?
post in ask gambler , but one thing for sure, there is a very tin chance that you can get your funds back if the site is truly scam .