There's quite a bit of grinding yes but you shouldn't need to buy too many potions/soups to advance - you should gotta find the appropriate enemies in terms of power and fight them, andbuy gear.
A few tips:
- you should try and keep track of the likes of enemies - for all of them there is one move at every stage which, assuming you time it well, gives them a lot of heat. It should fill or almost fill the 1/4th of the bar on their own, if you get less than half then you should buy better gear and try again later.
- get a matching cock ring + butt plug. There are vendors that sell butt plugs, and the blacksmith (unlockable character after beating a boss; faaairly early but can't rmb exactly where - think I used one consumable in this fight) helps you make cock rings. Matching sets give a significant bonus.
- don't forget to upgrade your weapon every so often. You can skip some - I got the 2nd and then recently the 4th one?
