I have been sewing dozens upon dozens of dance costumes this past few weeks. This year I have even sewn a couple of costumes for the principal dancer, including her undergarments.
I did have some input into the design of this costume. The brief was a demi-tard with frilly legs. I combined a Jalie 2915 bodice pattern with a Kwiksew leggings pattern and added a flounce between the two. I modified the Jalie pattern to ruche some of the panels. I added frills to the bottom of the leggings, which are above-the-knee in length. It turned out rather cute. I did not choose the fabric. I imagine that there will be nowhere to hide under the bright lights in this white lycra.
To determine the attachment line on the leggings, I tried the leggings and bodice on the dancer and marked where the bottom of the bodice sat on the leggings.
I had a frilly elastic that I used along the top of the bodice.
It turned out to be rather easy to gather lycra for the leg frills. I just used a long stitch and a high thread tension and the frills gathered by themselves, no pulling of threads required. I attached the frills to the leggings with a zig-zag stitch so that the legs could still stretch.
I did not hem the legs or the flounce.