My fall coat is this:

https://www.amazon.com/gp/product/B008JXFDXY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Because it's mostly wool, it's warm, but the material is fairly thin, so it's not substantial enough to be a winter coat (here at least). I personally like a mid-thigh length on my coats. I think it looks more adult, and saves my butt from freezing.