Your computer is only as good the parts that are inside the computer itself. If you have parts that are lacking or accessories that are falling apart, you experience playing games on a computer will not be as enjoyable as they could be. This is why I provide my most used websites for keeping my computer up to date on parts and accessories.
Newegg is the website I go to first when I am looking for computer parts. It was actually how I built my computer to begin with since it has such a large range of parts. Whether you're looking for a new hard drive, a better graphics card, or you want to revamp your cooling system with an RGB glow in the dark water cooling system, Newegg has what you need.
This subreddit is a good place to go if you're having trouble building a PC. If you don't know where to start, what parts to buy, why your build computer isn't working, there are many people who are more than willing to help you with any problems you have.
PCPARTPICKER is another website that offers a wide variety of parts to choose from and lets you find parts to build your computer like Newegg. However, the difference being that PCPARTPICKER is a little easier to maneuvre, and it also has a build guide section. This section can also help you out if you are having trouble building your PC, which is always extremely helpful.