I'd advise against storing cameras
too dry. It depends on what type of gear you are storing, but I aim to keep most of mine at a relative humidity of about 40%, which is dry enough for fungus spores not to germinate, and for any existing fungus not to grow, but not dry enough to destroy organic materials, such as leather. I monitor humidity with
these hygrometers (cheap enough to buy in quantity). Obviously you cannot expect gauges of this "quality" to be accurate across the range, but you can calibrate them to be accurate enough at the humidity you are interested in: I set mine by putting them in a sealed container with a bowl containing a saturated solution of potassium carbonate (both crystals and liquid are present), which produces a RH of 43%.
Camera cases I keep (at ambient humidity) in the sort of stackable lattice-sided plastic sided trays that supermarkets get some of their veg. in.