This was a super easy project :)
Take a tshirt, and cut it off around the middle (just make it about as long as you want your skirt to be.
Try it on inside out, and pin to your figure.
Sew it up with a zigzag stitch, and then sew the two edges down with a loose straight stitch.
Now cut another full loop from the shirt and pin the edge of it to the edge of the skirt right sides together.
Sew with a zigzag stitch.
Now fold the strip over and pinch that edge to the 2 pieces you just sewed together.
This makes a really nice waistband (kinda shown in my last picture)
Now pair it with a loose shirt and you look awesome!