Im likely to see a pattern here, where you can find 1-2 kind of balls (poke + great for example), 1-2 kind of potions (potion+super potion i.e.), one or more 10% type damage item (black belt, charcoal, miracle seed...) , Repel of different kinds, rare item of location (mostly evolution stones, sometimes things like nuggets, everstones, etc) and a variety of berries. Some items seem also be there for fitting the location like the mushrooms at Mt. moon or pearls at icefall cave.