Myrdin> Yeah, you're right. I did the same and now I'm overflowed with stamina potion. But I said that because evolution/blooming maps should shows up soon. Last one was a while ago and I will not be surprised to see it during next month.
At low level, you can still rely on level up to refill your stamina. Bonus stages gives a lot and manyu key stages are a good option too to get XP for 0 stamina.