there is no sure win in gambling, if there is, you wouldn't see any gambling sites today. it is surely pure luck but mostly you won't win against the house because of the HOUSE EDGE
You can beat the house but most people don't know how to do it. This is why gambling sites exist. The majority of the people don't know how to beat the house and lose money. If you know how to beat the house you can make a nice profit like 50%, but it depends on the game.
you can't beat the house edge, this has been discussed too many times already in this forum. users even provide proofs that no one can beat the house, you can win but surely in the long run you will lose your coins so better know when to stop if you are in profit