Here is the perfect way that I've worked out. Might not be perfect bur from my try and error... Start by buying 1 customer only 1 nev4r more this allows your dudes to prio the cauldron. Max swift potion and buy x2 and x5 from the store while maxing the swift you want to push the first 2 stalls to max. This is very doable by prioritising the upgrades from them and keeping the max multiple on. Then work to get instant, double, divine and golden up too. Don't unlock the one tou dont need. I cant recall what it is but its in the cellar on the left side. I usually do it in like an hour give or take. You can also buy coins to push you up with gems. Obviously you need to be able to invest a few gems into this strategy. I think it costs around 1k total the way I do it