>>287900750
Find a similar looking model, then change hair, clothes, eye color etc.
There is a Kuro base from Fate//Prisma on mmda.booru.
Maybe that can be used as a start? Still alot of work thou.
Browse models on 3D.nicovideo, mmda.booru and seiga.nicovideo to find parts you can combine.
Doing it from scratch will be a hell of a learning curve.