Hello Alice,
Well, to be honest with you the best way you gonna achieve the “right amount” is by having more and more experience and going through technical stuff in photography field.
I dont want to be rude here, but RC is not (in my point of view and if you want measurable and reliable data) a friendly software you gonna learn in one or 2 days, because there is so much knowdledge you need before. I’m using RC since end of 2015, and won’t say i’m mastering it.
Also its hard to say what is “sufficient”, highly relative on people, and what they need to do with the scan.
Did you had a look on the help section of RC, “How to take photo” part “Level of detail and precision”? great tool for distance placement.
How are you taking your picture? (iso, aperture, focal length?) so i can maybe improve your setup. depending shoot contxt, objects it can be very different, hard to tell without a clue ^^