Jeanie - Your Calathea's roots were damaged during the repotting and that is why it is hard for you to get a handle on watering it. The potting mix that you used was contaminated with fungus gnat larvae, which feed on decaying organic matter such as compost and bark chips, as well as rotting roots.
You can try to keep it as is and allow the soil to dry as deep into the pot as possible to deprive the gnat larvae of the moisture they need to survive. As a more serious alternative, you can gently undo the repotting by removing the soil that you added. Then, put the original rootball into a pot that is just barely large enough to hold it snugly. Fill in any spaces with a soilless peat-based potting mix. You can make your own by mixing 4 parts of peat moss with 1 part perlite.
