Really depends on which game you are playing, over time the house edge usually tends to pull back any short term winnings. I think that if you play a PVP game such as poker and its variants then you have a fair chance of winning if you are playing carefully and with tactics. Definitely stay away from games based solely on luck as you will end up losing in the long term.
It is the nature of gambling that at the end all gamblers lose their money. The ultimate benefit is of the owners of casinos. Gamblers never take any extra money with their selves, even they lose their own. Gambling is a bad thing and a bad thing has always bad results. You can never take any benefits of such a bad thing. Gambling is like a drug addiction and if you become gambling addictor you will lose everything.