Speaking as advice toward drawing in general, reference everything. Pick a pose you like, on a model you like, and sketch that. Then pick what parts you want to be decaying, which you don't, figure out how that changes from your model. Once you've got that down, find references for all the changes, as close to your base model as possible, then tweak. Keep referencing. Hair, eyes, skeletal structure, everything. Once you've done that, seek out texture and color references. When you're done with everything, keep referencing.
And then reference a bit more, to make sure you've got it.
Then, once all that's done, put your own style and ideas to it. Reference these too, just to have a good basis in reality. After all that's done, you should have a very pretty, very well-finished piece on your hands.
Then look up more references, just to be on the safe side.