At 4th Gambit event (last Gambit) at end stage each spin costed 7 stamina and every 8 spin players had a 2/6 chance of getting a reward. So 1 reward per 168 stamina.

At 5th Gambit event (this Gambit) at end stage each spin costs 9 stamina and every 16 spin players have a 2/6 chance of getting a reward. So now 1 reward per 432 stamina.