Theoretically, you should always be able to win if you kept on doubling your bet. But that's exactly the problem. No casino owner would ever just sit back and allow you to double your bet endlessly. That's why there are limits set in place. In case there aren't any, and if you actually do start winning a lot, you'll definitely be asked to leave.
A typical casino slot machine payout rate would be somewhere between 82% and 98%. Thus the more you play, the more you will theoretically lose.
If you ever do try gambling, make sure it's just for the fun of it. Don't expect to earn anything and be prepared to lose whatever you're betting.
So if you are ever in a financially tight situation, gambling is seriously the last thing you should turn to.