If you have a large sum of Bitcoin and you bet low, martingale actually works, but what makes the site overcome it is the natural tendency of human to gain more and fast. If you really stick to the rule, you earn but it would need a lot of patience. Martingale works in every odds. You just have to adjust the multiplier.
But seriously, think about it. You're risking all your bankroll just for this tiny base bet and profit? Like, if you have 20 BTC, and you bet 1 satoshi per bet, there is still a risk of you busting, as anything is possible with chance, especially if you run it for long periods of time.
So no, there are no real safe methods to gamble, unless you can find an arbitrage opportunity.