Stick to your profit goal and loss limit. When it comes to roulette and any other gambling game, you should only bet an amount that you know you can afford to lose. Once you've decided how much money you're willing to lose, stick to that amount and don't be tempted to bet any more. Things can get out of hand quickly, especially with a game that goes so fast.
The first time I tried Broadway Roulette we received tickets to Beautiful. Our tickets were in the back of the orchestra which I wasn't thrilled about, given that the theatre was mostly sort of empty, and that ticket prices at the box office started around what we'd paid for using the service. Similarly, my second experience garnered tickets to The Prom, which I loved, however the seats were in the mezzanine and, when all is said and done after the fees, the ticket price was very close to (if not more) the starting price for tickets to see that show in the same section.
Even if there isn't a betting limit, and if you have an infinite credit limit, it still doesn't really work, it just doesn't really fail either. If the martingale strategy is continued indefinitely and without regard to betting limits, your bankroll will hit arbitrarily high positive and negative values. The expected value is still negative, but the variation is so high that it your bankroll won't stay either negative or positive.