Send data to a PC

I am a gamer but also use arduino. I want more Thumb mouse buttons but only have 2. A new mouse costs aroun 52 euros, very expensive for a 13 year old boy like me. I want to use arduino to add extra thumb mouse buttons i can also usi in games. Do someone have a solve for me?
All help is welcome and thanks for it,

52 Eu is awfully high for a mouse! Can you or parents get eBay? Mouse is far cheaper there.

Arduino Micro has a USB AVR for the main chip. It can be coded to act as a USB HID mouse/keyboard/joystick, that is what the PC will see.