Slots are rigged, the casino decides how much it pays and how often it pays. They decide how much you are allowed to win from the slot, for example the slot let's you win 1000$, after that it's 100% certain you will lose all of your money since the slot is programmed to stop paying you after a certain amount. Only intelligent way to do progressive betting on slots is by switching the slots machines you play on while maintaining the bet progression.
The likelihood of winning anything big on slot machines is still rather low even with progressive betting.
Play blackjack instead, if you are smart and have some luck it's quite easy to 10x your bankroll rather quickly.
If you wanna play it safe you can either do martingale (with a bankroll that you can afford to lose), or card counting. Card counting works fine but it will take a lot of effort and time.