I can not name any gambling site on which it is possible to always receive a win as it depends only on luck. Now you can use any crypto currency for the game, but do not spend all coins on entertainment.
You can not name any gambling site on which it is possible to always receive a win because such gambling sites never existed. Victory is not determined by the site but is determined by how lucky we are in gambling. That's it, none of the sites can make us always win.
It is not the case with only gambling sites but land based casinos do the same with its players. That is why; no gambler on the face of Earth can claim to win 100 percent of the times in his life. Gambling is a random game. In few games, the control is in our hand but even there we need a little help of luck. I think, if someone is losing a lot on one site, changing it won't do any good.