I found this game hilariously bad when it comes to character progression.
All characters have but 3 stages, which you reach quite fast, by fetching items basically. Once you gain all 3 stages, you have sex and you can henceforth have sex anytime you want. As you might imagine, between these 3 stages there is little room for any real depth whatsoever.
And, well, that's the corruption progress. By stage 3, one would assume that the girl is starting to get interested in you, yet that's the point where she wants to have full-on sexual intercourse wherever, whenever (despite even being married lmfao).
As for the management itself, once you get the automatic waterers you pretty much have infinite money. You don't really need anything else except for quests. You can just plant stuff, sleep until they're ready, then replant and sell the surplus, repeat.
There are no upgrades, no XP or skills. You pretty much buy stuff with the money I described above. And there is just one level to gain for each tool (apart from the axe, if I remember, that has a middle one as well).
I mean, it's fun I suppose, if you have an hour to spare, but I never found it hot, despite the cast of characters.