Hypothetical scenario:
You can bet on a single dye roll (choosing a number between 1-6), but if you win you get paid x12 of your stake (instead of x6).
So the Expected Value is positive (see example below), but you'd still have 83% chance of losing.
1 - will you take that bet?
2 - if so, what % of your available funds would you put at stake (i.e. funds you're willing to gamble and afford to lose)?
Again, this is a single, non-repetitive bet.
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Simulation for BTC1 bet:
EV = (83% x -BTC1) + (17% x BTC11) = +BTC1.04
Edit: calculation corrected, credit to Saint-loup
I've tried, actually the chances of winning are even at 80% but I still lost, how much more than 17%.
Maybe that's possible if you have a lot of money to lose gambling.
But if you're just going to gamble to grow it and maybe you'll get lucky, I think it's a bit vague and too risky.