Light-these plants only need a moderate amount of light.
No direct sunlight needed filtered light is best. Too direct of sunlight will change the leaf color and cause burning of the leaves.
Your soil for Calathea should be highly organic and well drained. Use plenty of coarse material in the soil mix to help water flow through. A commercial cactus mix is fine
Never allow roots to be soaked with standing water but they do enjoy continuous availability of water in their soil. Water often to obtain this condition (with perfect drainage)
You can propagate these plants by separating them into sections and pot the sections. Do this in the spring when you check them for re-potting.
These plants thrive with humidity you may have to create an artificial environment to accommodate this. This is done by putting the pot on a tray filled with rocks or pebbles. Also, you can actually just run a humidifier near them.
Remember, this is a jungle plant