What is a fair sample size to know if you've found a strategy you can lump on?

[Michael Caine]

I've spent a lot of time over recent years trying to find a betting strategy that will make money. My aim was 10%. However, over my last 137 bets on my latest strategy I am up 21.18%. I am betting 10 pounds per bet as I feel it is a work in progress and far too small a betting sample size to be sure that I have found a system that will pay long term. So what do others who can relate to finding a betting strategy feel is a fair betting sample size to start really raising the betting stakes?

[MVidal]

I believe that the ideal sample size to validate a method is 500 bets making entries without escaping your bankroll management, from the result you can draw conclusions as to whether your method is profitable in the long run or not.