I like historical costuming. To me its like a puzzle trying to figure out an aesthetic and recreating the look. I try to make my things on the side of authentic. That said, there are things I am lenient on. Fabrics that look good on a human does not always work for a doll. Reproduction materials are not always affordable. When it comes to the proper undergarments, my dolls don't wear very many.
The purpose of the shift is to keep sweat, oils and other bodily grime off of the good clothes. Dolls do not create these things, so I usually bypass this layer. Depending on the era, I don't do corsets either. Resin is not squishy, so corsets would fail to compress and lift.
I do use petticoats though. It effects the hang and fluffiness of the dress, and I enjoy decorating them. Here's an example: