I have seen many people have made models with ball joints but yet do not see a posting for how to make them. I myself very interested and would like to make my own, but not a hundred percent sure how to go about it, and I really don't like the idea of messing it up. So if anyone out there knows or has a suggestion let me know.
Ball jointed dolls use ball joints, but not sure this is the route you want to go. you probably want something more like monster high dolls. BJD use ball joints but need to be strung together. There are plenty of explanations on these joints online if you look. You could also buy a similar doll and dissect it or take a look at how others use these types of joints.