How I would play
I would probably play a 2:1 payoff game. I would most likely play the dozens on roulette using a (gasp) martingale. Start with a $50 bet, if lost then go to $100, if lost go to $150. If the 150 loses then at least the rebate should pay you back, thus eliminating the negative expectation still usually associated with a martingale. I would not play this very long as you can bankrupt pretty quickly and sacrifice any winnings back to breaking even. Probability says you win slightly less than 1/3 of the time on the dozens, but with no risk, the payoff can get you $150 or better pretty quick. Hit it and quit it. That $300 won't last long this way, but with 0% risk, go for a high, yet still probable payoff, and then get your money and get out fast. I prefer this way because of the possibility of a quick high payoff or at least a fast final decision of breakeven.