Multiplying the bet amount by 7 times isn't bad at all. I thought about applying this strategy to other games, like roulette, betting on black or red, even and odd, 1 to 18–19 to 36, for example. Splitting it into 3 larger bets, approximately 33%, on each, instead of choosing one number, which pays more, but is also the most difficult.
It may not be feasible, but OP's strategy gave me some ideas…

The dilemma is if you are playing luck-based games like what you mentioned, roulette, you are still relying on your luck. And you can even lost all your succeeding bets and not win at all. What are the odds, right? So I won't be very confident that such strategy may give me winnings. Always consider the side that you can lose all your bankroll in one sitting.