Example: bet $1 - lose, bet $2 - lose, bet $3 (instead of $4) - lose.
NB! If you are afraid of the losing streak, you can minimize your losses by putting the 3rd bet on the summary of the first 2 bets, not the 2nd bet's double. You can only lose if you are on a lose streak for 15 times, then the amount will be bigger than the bet limit ($50,000). It is hard to lose, but remember, you do not have infinite money, so rather start small and build your way up. The idea is that eventually, you will have a winning spin that covers all your previous losses, and each win will double your initial bet. If you lose again, you double your bet to $4, and so on. If you win, you go back to your initial bet of $1. If you lose, you double your bet to $2 on the next spin. Let's say you start with a bet of $1 and you choose either black or red (in Roobet it's grey or red). Not like a classic one with 37 (0 to 36). Roobet Casino is the best casino to do it, because their wheel don't have numbers and it is only with 14 slots. I have used the Martingale system successfully in Roobet.