This is an interesting Outside Bets system that we have come across that combines even money bets and dozens bets (you can also play the columns of course).
You bet on an even money bet- say evens, If you win, you keep your money on the table (let it right) but movie it from the even money bet to 2 dozens (or columns).
So for example you bet £10 on even. Your bet come in, giving you £20 on the table. You then use this to be £10 on each of 2 dozens.
Say you lose the first bet on evens. You then bet £20 on evens. Let's say you lose that one too, you would bet £30 on evens. If you lose again, you bet £40 on the same and you win, so you now bet £40 over two dozens. If this comes in you will be ahead overall by £20. At this point, you revert back to your starter bet.
If you lose the dozens bet, you then bet £50 on an even money bet if you wish to continue the progression up.
This system is interesting in that it gives you a less aggressive progression on the even money bets, than say the Martingale, which it then tries to make up with a final dozens bet where you are covering almost 2/3 of the table. The idea is to try and protect you from those incidences where you see results repeated more than 4 times in a row- the kind of situation that normally sinks a Martingale player.
On the downside, it is by its nature a system that tries to grind out profits. The trouble with these kinds of systems is that you are by definition at the table for longer periods. And if you are at the table for longer, you have more chance of falling foul of the natural law of roulette in which the casino nibbles in to your bankroll at every spin.
Some people play for repeaters in the early stages when they are making even money bets- so if they see 2 reds, they will bet red for example. Some people do the opposite- it doesn't make any difference from a probability point of view, but we prefer to have some sort of betting system and stick to it- it can be maddening if you are choosing bets at random at the very last minute and you hit a run of spins that goes against you every time.
When you get onto the Dozens Bet, again have a system- either bet on the 2 that didn't hit on the last round, or go for a repeater. But make your plan and stick to it, and then you can concentrate on playing the progression correctly.
The whole idea behind this system is the belief that winning on an Even Money bet and then on 2 dozens is more likely than winning on 2 even chances consecutively (because you are covering more table over the 2 bets). However, like any system, it will break down eventually and your main enemy is the time you spend at the table. At some point, you are going to experience a run that goes against your bets. The aim of the game is to hit your profit target before you get there, or at least identify the bad run and cut short your losses.