I like your idea, a cute demon prince, it's a nice design! If you want your drawing to be less messy you can always work on your line work, do multiple pass by tracing over it or cleaning it in photoshop [or others image software]. For the texture, It's like Milan said, it's the cherry on top of your drawing! You need to work first on perspective and a good start is observation drawings of 3D objects, detail need to come last... sometime you don't even need it! Keep drawing, have fun and it will come naturally don't stress over it! And it already looks like you are on a good start.