I used one a shirt that is getting a bit snug to draft a pattern for the top and made it a bit bigger, and added the peter pan collar. I am loving peter pan collars on her these days.
I went with blue buttons down the back for a little pop of color.
The leggings took about 10 minutes, leggings are about the easiest things to sew. The knit fabric I had is super stretchy. You can't see it in the photos but they have a roll over waist, like yoga pants.