There is no better way to learn about wearables and electronics than trying your own project. Adafruit has published a guide that shows you how to create your own NeoPixel LED Cortana Costume with Gemma. You are going to need NeoPixel Rings, conductive thread, a Gemma, and a rechargeable battery to get started.
The above video offers more information on this project. More instructions are available on Adafruit.