Well, first and foremost you need a strong computer that is able to run the majority of video games these days, in high settings.
Apart from that, you will need the usual equipment used by most vloggers who operate from home – a camera is a must, of course, a good lens won’t hurt, and additional gear for indoor recording is always welcome.
Some gaming YouTubers don’t record video footage of themselves while playing and only focus on adding audio commentary over recordings of themselves playing games. Engagement is always stronger when users can see you, but it’s a start.