This is a good question, but it is very hard to give a definite answer. Different questions required different types of data. For just presence data, some commonly used resolutions are 30 m, 100 m, 500 m, 1000 m (1 km).
But scientists also use iNat data to assess behaviors, phenology, and other kinds of things, so there’s no hard and fast rules about predicting what could be useful. That’s why some folks have answered that you should do what you enjoy - if you stick around and keep adding observations because you enjoy it, there’s probably more chance of making a contribution in the long run.
In my personal experience, I would generally say that I tend to observe one of each species at whatever I am considering a “site” in my mind at each trip there, and more if something different presents itself (different life stage, behavior, etc.). But this is largely because I just want to remember what I saw on any given day, not because I’m trying to anticipate what might help scientists.
There are some previous threads that address similar questions that might be helpful to look over as well, e.g.:
https://forum.inaturalist.org/t/what-is-a-good-distance-to-add-the-same-species-again/4098