|This is a great shortcut for a beginner. If you haven't yet mastered collars, set in sleeves and facings, but can make a skirt, then take this shortcut to an "Advanced" design.
Buy a jean dress or shirt RTW. I got the one in the photo in a thrift store for next to nothing. Cut it off slightly above your child's natural waist. Then cut a fabric rectangle about 2.5 times longer than the bottom width of your cropped shirt. It should be wide enough to reach your desired length plus a hem. Gather the top using a double row of basting stitches. Pin it to the shirt bottom's raw edge and pull up gathering stitches to fit. Sew it on and presto! A fancy dress in next to no time at all. For the sample in photo I also added a belt and side ruffles.