From my experience martingale never works. For it to work, you need an unlimited capital and a house that is not limiting your bets. Even if you have the capital, most of the casinos/betting sites will limit the amount you can bet. In theory you think, yeah it is very unlikely to see a 14-15 losing streak but in practice that shit happens, more than it should.

You should just gamble for fun and with the money you can lose.