The lower right cell shows a house edge of 10.65%. I do not know what is the most common win, but the following return table shows the odds for a win of 150 to 1. There is also a version of 2G'$ for triple-zero roulette. Divide that by the one-unit original bet and you have a house edge of 5.33% by parlaying, relative to the initial bet.
You can either bet on the odd numbers or the even numbers. Odd or even: It’s one of the easiest and simplest bets in all of roulette. If the player parlays, his expected loss between the two bets is the sum of 1/37 = 0.0270 units from the first bet and an average of (1/37)*36*(1/37) = 0.0263 from the possible second bet for a total of 0.0533 units. High or low: The high or low entails betting on a number sequence from 1 to 18 (low) or 19 to 36 (high). The answer has to do with the way the house edge is defined. The astute reader may wonder why the player should accept a win of 1,300, at a house edge of 4.97%, rather than parlay, when the house edge in single-zero roulette is 2.70%. Thus, I would do that rather than accept a win of 1,275 or less. By parlaying a first win on zero himself, the player can achieve a win for two consecutive zeros of 1,296 to 1.
