I use PicsArt and Ibis Paint X!
With Ibis Paint X I can add contour, eyeshadow, and blush to the characters on the cover. I can also draw on the clothes with Ibis Paint X!
On PicsArt I can make my backgrounds and add the title. I can also make my characters into stickers on it and place them on the backgrounds.
These apps are both free, and I definitely recommend them!