>>5977524Alright. First, you need a solid background in sculpture. If you want to do ball jointed like your OP pic, you're going to need some solid reference for how they work(I know modern resin BJDs are strung with elastic, no idea if the same is true of porcelain).
I STRONGLY recommend you avoid the aesthetic of western dolls. Most of them have extremely uncanny faces, and very weird body proportions, making them look fucking weird at best. You're better off drawing from real people, and keep in mind that dolls don't NEED to be painted before firing, and using a combination of pastels and paints after the fact can achieve a much better result.