while this potion has the highest chance of complete failure, it averages a profit on the long run (which explains your hardship).
in an attempt to bankrupt in the least amount of potions i have found this stategy:
at $10 to $35: brew the previously mentioned potion
at $40 to $55: brew a vinegar + green slime + green slime Slime Potion
at $60 or $65: brew a water + dandelion root + bat wing Strength Potion (you may choose to skip this one, it only costs you 10)
at $70 to $80: brew a wine + blue slime + blue slime Slime Potion
at $85 to 100: brew a green slime + lovage + daydream Potion of Lesser Healing
at $105 to $170: brew a blue slime + daydream + bat wing Potion of Invisibility (this one is guaranteed to cost you $25)
if you find yourself unlucky enough to have $175 or more: brew a rose + cilantro + spark of hope Love Potion. hopefully you'll be able to bankrupt on the second or fourth potions on this list, which is quicker than the first. the other potions on the list are focused on losing money over time rather than immediately
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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.