I recommend making a small game like Cookie Clicker, which is a game where you click on a cookie, and it increases a score. After a certain amount of points, you get a powerup that automatically increases your points.
You can make this by making a part, and making it so that if you click it, another part is created that is parented to the part that you clicked. Then, you make it so that the part that was created will be destroyed after a certain amount of time.
Hope this helped!