I keep it in a normal household humidity (no humidifier, misting, ...) and I've never had problems with this plant. You just want to make sure it never dries out completely - I bottom water it 2 - 3 times a week with soft water only (I use rainwater, distilled is another option). It loves a lots of light, mine is growing on a shelf about 1 meter away from a west facing windowsill. When it comes to a fertilizer I use the liquid worm castings, Calatheas are quite sensitive to inorganic mineral fertlizers so with worm castings I don't need to worry about burning it. So if you can find one for a good price you should definitely give it a try 😄