If you're looking for a free program to use layers on, I recommend
GIMP or
paint.net; both are good, GIMP has proper brushes while paint.net is a little easier to start off with (imo)
I love your art!! It's extremely cute and I value the personality as much as technical skill, which will obviously improve as your practice. My favourites are the Gen VI starters and Vitalimar
p.s. luvdisced.