Do you have to buy a gamepad for the Nintendo Wii U to work?

No, the Nintendo Wii U can be powered on without a gamepad and a Wii remote can be used to open applications and games on the Wii U. However, it is strongly recommended to have the Gamepad because all Wii U games are compatible with the gamepad, but not all Wii U games are compatible with the Wii remote and classic controllers