This top has an asymmetrical hem and flattering diagonal stripes. I made mine out of two unwanted shirts, but any knit fabrics would do nicely.
The leftover scraps became a fun, braided headband that matches the top perfectly.
Step 1: Cut your shirts into strips
Try to start out with really large, long shirts if you can. It's always nicer to have plenty of extra fabric to work with, and you'll be losing a little bit to seam allowances anyway. If you're using knit fabrics instead of shirts, cut the strips so that they stretch crosswise, and not lengthwise.
Select two coordinating t-shirts and cut off the sleeves, hem, and collar. Make lengthwise (hem to shoulder) strips out of the front and back of both t-shirts.
I made strips that were 3 inches wide and 19 inches long. I needed 18 strips to make the top as long as I wanted it, but you can certainly keep adding and adding to make a dress! You could also cut wider or narrower strips to suit your taste, or even use three or four different shirts.
Be sure to save those scraps from the sleeves; you'll need them in a few minutes.