Add a chain of NeoPixels to GEMMA's GND, D1, and Vout pads. Any NeoPixels will work just fine (strips, sticks, rings, etc.) but in keeping with the textile theme of this project, we'll be using individual sewable pixels.
Start by stitching between GEMMA D1 and the data input of your first pixel. Knot the thread at each and and seal/snip.
Stitch very long strands of conductive thread to GEMMA GND and Vout and stitch each up to - and + on the first pixel. Knot the threads at the pixel but do not seal or cut the leads short. Instead wrap the excess threads around bobbins or scraps of paper to keep them out of the way.
Stop stitching after each pixel to test your stitched connections.
Eight pixels stitched around the inside of the hood: