I saw a turtleneck midi dress from Forever 21 that looked like an easy enough dress to try and emulate and it was basic enough that it seemed like a great first project. And obviously, F21's price point is super affordable, but a couple of yards of grey fleece at less than $5 a yard is pretty hard to beat.
2 yards non-pill grey fleece
To make this dress, you'll need to cut out two pieces for the back, one front piece, two pockets, and two pieces for the turtleneck. I measured myself and made the pieces pretty close to my own body shape because I wanted it to be a bit more form-fitting.