Powering the Board
I chose to power the project with a 9v "wall wart" power supply. Check the specs on your Arduino-compatible for what power you can give it
You can also power the project off the USB port. This works well for portable installations: just plug it into a USB battery
Powering the NeoPixels
Normally, the 5v output of an Arduino is not adquate to power 16 NeoPixels, but in this application, the total brightness of the ring is limited keeps the current to to safe level.
I've added a resistor to the data line as suggested in the Adafruit NeoPixel Überguide.