I managed to do it with a Nightmare + spark of hope potion of game development and a Red slime + Nightmare + eye of newt invisibility potion! Only used the red slime because I needed 5 more to squeeze out of this potion, but it worked out.
It's more risky to go for the Invisibility potion at 40 because you get more money if it succeeds, but there's a higher probability it fails, too. I find that it's worth it because it's easier to lose money the more money you have by using love potions (though I prefer daffodils in mine)
I also found I really like the Blue slime + Daydream + Eye of Newt Invisibility potion because not only is it a guaranteed loss (albeit only 5), there is a slight chance to lose all 85 coins in a single potion. And given you can repeat brewing it a lot, it *will* happen eventually.