You do not need to purchase a remote. I had similar problem, just find a way to solve it.
- First, you need to have a Mac and a wireless keyboard in order to do this way.
- You have to reset ATV to factory default first - you can use micro USB cable to connect ATV to a Mac and follow the process to restore factory default.
- Then connect ATV back to TV, it will prompt you to use store setup process and give you a chance to pair ATV with a bluetooth wireless keyboard
- Once the wireless keyboard is paired, you can follow the steps to set home sharing and remote app again