I always say start simple for photoshop and build your way up. Its like if you were to attend guitar class for the first time and you don't know anything about guitar, but then bit by bit, he gives you a new chord or song to practice. Drawing in digital will be the same challenge as any medium which is "figuring it out" and just by drawing visually rather then the computer to do totally for you. So start small, and limited. See how far you can take just with the round circle brush. After awhile, look up what layers are, what the eyedropper does, etc.