So here's what I did:
-1 piece of wide elastic
-needle or sewing machine
First, cut 2 large rectangles from each of your two t-shirts by cutting off the sleeves and collar and then cutting anything else you need to make the edges strait.
Basically, just sew the rectangles together, alternating in color.
So you have a big tube.
Then turn your head to the right because I was having some trouble uploading pictures to blogger, and sew the elastic to the skirt(I used the waistband from the pants I was using instead of one of the t-shirts). While you sew the elastic to the skirt, pull the elastic so that when you sew, the fabric will ruffle up.