Here's the system I've come up with. It's a riff on the Blackjack system which I forget the name of, where you double your bet if you lose and halve it if you win. You bet on one single number on Roulette, and increase your bet steadily (by at least ~3%) until you win. Bet somewhere between once per day and once per week. The less you bet, the better your odds of winning. The more you bet, the more you lose. You're all but guaranteed to win eventually and claim a profit, it could take 1 spin, it could take 200.
The key is to choose the right sum of money. The amount at which you can afford (and afford the increases) but the amount at which a win is meaningful to you. Also the time of the investment is to be considered, if you're doing it just once per week it could take 2-3 years to complete (at worst).
eg. you bet £10 on the number 1. If you lose, you then bet £11. If you lose, you then bet £12. Then £13, £14, £15, £16 and so on. The odds of winning are 37/1 and the return is 35/1. So if you win after, say, 11 spins, you've invested £165 and you win £700 (20 x 35). If you win after 20 spins, you've invested £390 and win £1015 (29 x 35). It is perfectly possible to lose for several hundred spins in a row, though, so you need the money/time/balls to commit to it. And it's important not to pick a figure too high, which stretches your finances.
Once you win, you can either stop or start again.
