When it comes to slot machines, it's virtually impossible to come up with a real strategy because they operate on a fixed algorithm. And even if you somehow managed to understand that algorithm , which is highly doubtful and unlikely, it still wouldn’t allow you to win consistently. So building a strategy around such games is a myth and self-deception. I can confidently say that not a single millionaire has been made this way, except the casino itself. The only real strategy here is to clearly define the amount you're willing to spend on a game of chance. If you're lucky, you win. If not ,well today just wasn't your day.
Not virtually impossible, but just impossible. At least with the online slots.
I know of a one local case where man managed to find patterns by analyzing video material of slot playing in physical casino. Casino didn't explain how he did it, and they sued him for cheating. I wasn't only one who was very surprised about the fact that he had to pay back the casino. This makes me think that there was something more then analyzing going on. Maybe exploiting a bug or something... What ever it was, it wasn't a winning "strategy" in sense of the word.
Someone could look my gambling history and say that changing strategies have brought money, but they also might have caused me lose money. And in the end i don't believe that strategy has nothing to do with it. It's just a confirmation bias in action.