3x S&P, it moves fast. Just martingale into it as it goes down, but plan things so that you never use up all you money like idiots who martingale in Forex do. Adjust your TP after each entry, leave a % as a runner in case you catch the beginning of a trend, you wouldnt want to close your position and then miss a 50% move (like 17% corresponding SPY move) to the upside before a retrace. then start over every time price declines a certain % and recalculate your entry prices so you don't use up all your money. Why wouldn't this strategy work for long term gains? You know the S&P will always eventually recover, and the martingaling into it lowers your BE point and allows you to profit even if it never gets back up to its previous high levels.