I followed this strategy in many times specially in CASINO but i lost big amount of money, because you can't win every bet. Even i waited 15 times then i have no dollar to bet for next one, as a result i lost everything. So, i would like to recommend don’t start bet with big amount like 20$, you can start 1$ if you have big amount then start 5$-10$. There is a high possibility of losing everything if you get too greedy.
Martingale is not a good system because when you think about it, there is always a chance to lose, and when you do, the loss will be greater than your previous winnings. This means that over time, you will lose more than you win. The only reason why this system can seem like it works is because people tend to have winning streaks and losing streaks—but the Martingale system won’t help you avoid losing streaks.