Just like Csyui said, one locked crate a day is good enough for all your potion problems. If you have an extra hour free one day, farm like 5 lockeds and then you can either have some profit, or have a reason to not farm them the next couple days. If you're really worried about potions, you probably should do dailies. Another thing is, why are you trying to earn more character slots? Not the best idea to make more characters if you can't afford pots for one.

Sent from my SAMSUNG-SGH-I337 using Tapatalk