"onesie shorts from an old t shirt. I didn't like the romper, so I made my old t-shirt into a baby one. Just follow this tutorial" until you get to the part that you're supposed to make the legs, cut off the bottom, and hem the ends to make it a tee.
Yoga Skirt Tutorial (Toddler Child Women). Soft folded waistband with a knit or woven twirly skirt panel. Tips for working with the knit/woven combo, plus general guidelines for getting the measurements right.