oh goodie
first do a blinking light to get your self good with the language
make sure you have a few breadboards hundreds of jumpercables and tons of LEDs/Resistors.
Get a Servo because they're cool.
I did something where I click a button turn off the lights and leave the room for dinner and when I come back I turn on the lights and it turns on my computer.
You should probably get your self good with multiplexing because that is important.
Try doing something like turning a potentiometer to determine the brighness of an LED.
Try using a buzzer. Try messing with photocells.
Try something like what I did, Arduinos are supposed to interface your code with real world objects.
