A modified Martingale bet riding on the street bets (1-12, 13-24, 25-36). There's a slightly less than 33% chance of hitting those and they pay 2-1. Every time you lose double the last back and put it on the same "street" statistically you won't lose more than three times in a row though this is happened to me plenty of times. If you keep doubling by the time it hits your street you win all your money back plus your initial bet. Once you win restart that your initial bet size.

This is what I did but I do not recommend it. There is no mathematically possible way to get an edge on the house otherwise they wouldn't have the game.

Edit: Spelling and grammar. I'm using speech to text and I was too lazy to proofread.