People make the mistake by putting plants in huge pots. This is not necessary. If they are actively growing, then no need to transplant until you see roots coming out the bottom of the pot.
When transplanting, move to one size larger than the pot previous.
Water in well drained soil, perlite. Let water run out of pot, do not let water stand in dish under plant. Dont water again until the top of soil is dry to about 1 inch below soil. Fertilize very lightly when growing indoors until you are ready to set them outside or in the ground.
Keep in sunny warm location.
Outside, bananas grow fast, and the need to transplant would be much higher than growing indoors.