I bought a tutu from Amazon.com that has 3 layers of tulle and a satin layer. I think they meant for the satin to go on the inside, but I turned it around so the satin was the top layer for better LED diffusion.  

To make the tutu into a tie-on skirt, find the seam in the tulle and cut through all four layers. (You could leave it as a pull-on skirt if you'd like, but this way it's easier to get in and out of and fits a wide range of sizes)

The edge you just cut is now the center front. I rounded both front edges of only the satin layer to make the tutu lay nicely on my hips, creating a "bustle" type look. Save the pieces you cut off! We'll use this extra fabric to make the battery pocket. If you'd like, finish the lower edge of the tulle with a serger or make a small hem.

Cut two pieces of white elastic or ribbon to make the ties. Sew one to each side of the tutu at the top, underneath the satin layer.

Grab one of the scraps of satin you cut from the front corner of the tutu. Trace around the Circuit Playground and battery pack to make a pocket. Cut it out along your lines. Finish the edges if desired.

Stitch the sides and bottom to the TOP layer of tulle, just underneath the satin layer, making sure not to catch the other layers when you sew.

With the electronics in the pocket, plug in your light strand. We want to attach the lights on the outside of the bottom (innermost) layer of tulle. To get there, make a small hole in the middle and top layers of tulle so you can slip the connector through and plug it into your Circuit Playground Express.

Sew around the wires between the pixels to attach the pixels artfully to the tulle. I like to try and stagger them a bit, so the lights look more random and it doesn't look so much like a strand.