There is no better way to learn electronics than building your own things, including smart wearables. Adafruit has shared another guide that shows you how to build a 3D printed pair of electronic sunglasses. You can control the dark tint from the glass.
To get started, you are going to need a LCD controllable blackout panel, 100 mAh battery, connectors, slide switch, and a few other parts. Knowledge of soldering and multimeters is required. More info is available here.