If you dont want to watch the whole video you can skip to 5:50.
This video explains how to get profit gambling with the Martingale Bet sistem.
In the coin flipping part, the flips are 50/50 as natsirt and squidward said, but there is still a chance of getting unlucky and losing 10 flips in a row (like in the example given in the video)
So, talking from experience, if you winning a lot of flips in a row, I would recommend start lowering the ammount of money you flipping after 3 or 4 flips winned in a row as the possibilities of you winning are getting lower, but if you want a lot of money and you dont lower the ammount of cash you bet and you lose, I wouldnt double the ammount of money you lost because it is likely to be a losing streak and you will end up losing everything.
This being said, the last advice I will give you is; if you dont know when to stop gambling, then don't gamble or just gamble small ammounts of money because you will lose everything. I know this from experience.