You can use Kelly betting.

The fraction of your bankroll you should risk on any try in a roughly even chance game = 2p-1

Where p is the probability of winning.

In the case of roulette p=18/37 so 2p-1 is 36/37 - 1 = -1/37 = -2.7%

The negative implies that your best strategy is not to bet at all, since it is a negative expectation game!

However let's assume your chance of winning was 52/100.

Now 2p-1 is 104/100 -1 = 0.04 so you should risk 4% of your bankroll on each bet.

If your chance of winning was 55/100 you should risk 110/100-1 = 10% of your current bankroll on each bet.

All the way up to a dead cert 2x (100/100) -1 = 1 or 100% of your bankroll.

This is really designed for a positive expectation game eg Sports betting where you have inside information, or advantage play where you have a calculated edge.

However, if you don't have an edge and still want to bet, and stay in the game for longest, or longer if you are lucky, you can bet 1% of your current bank roll. Or another strategy is just to make the minimum bet allowed.

If you want to risk your entire capital in a short period while having a chance of making some decent gains, then you could use D'Alambert or Labouchere progressions.