If Gambling is for fun then its not wrong but if just spend all your money in gambling like a crazy then it is wrong as it will make you loose everything.
When you really lose everything youve got then you are doing it wrong,many people do it for fun and when they profit its enough for them.
Just forget about the profit when you are in a gambling site and for sure you won't go wrong.. just think of it as if you are paying for the pleasure that it gives you, and if you win, just consider it as a giveaway..