Thank you for the advice. Do you know of any game that has no stats like you said and just story progression?
Seems like most of RenPy games have no stats, even if they are sandboxes.
The Headmaster, HS Tutor, Public sex life H, Harem Hotel, Peerless Lust, Corruption (by Mr. C)
But when they have stats, they are often used as a story progress indicator, instead of actual variable to grind. For example, you have a special event like training with a veteran warrior and your strength goes up, after that event you have new choices in dialogs, but training again with the same NPC will not raise your strength more.
Talking about progression indicators - these things are used everywhere, and they are mostly tied to specific NPCs or organizations. Things like "date this girl 3 times to unlock sex" or "rise your rank in guild to unlock new shop items". These stats dont interfere with new content when its added to a game, so they are safe to use anywhere.
What about money? Do you think getting money to buy different outfits or items for the girls is a bad idea?
Getting them new outfits is a great idea. But working for money - only if you have a good minigame for it.
In some games when you progress with the girl you can ask her to wear more revealing outfit, but you dont have to earn money for it. This outfit magically appears in her wardrobe. Also it may be a shopping date, where she tries a few outfits and you decide which one to buy. No money involved, game pretends that you have enough money in your pockets.
Same goes for other stuff: renting a new apartment or getting a car on your birthday - it can be a story event without money transactions.
BUT If you are making a simulation, not a story-driven game. Then you need proper stats, consumables, money and everything else.