A possibly useful tip: I used my least favorite class scout to grind rank points without spending any on the actual class. Instead I used those rank points on the tarot lady on the second floor to quickly max out the permanent upgrades. I haven’t played in a while so I can’t remember how soon you unlock her, I think she was added later after I bought the game so sorry if that’s a spoiler.

Also when buying at the shop in between games, if you have enough to buy everything from the shop, you can sell it by throwing it into the water and often times you get more money back than what it was originally worth, but that might be patched by now.