, and welcome! Linux is a lot like Windows... but it is NOT
Windows. Steam makes a Linux version, so many games are available... but I'm not a gamer so I don't keep tabs on what works, and what doesn't.
Since you're building a new computer and Linux interests you... the best advice I can give is to simply TRY IT
. When the system is assembled and you're ready for an OS, then look around here as there are already many instructions on how to install Linux (after you choose which one to begin with). For beginners, many of us would typically recommend Linux Mint or Ubuntu to get you started... and you'll want the 64-bit version when you pick one to download.
We can go through the install steps again, step by step, if you need that... but it isn't too hard. You download the Linux .iso file, burn it to a DVD or USB (has to burn with a special method so it will be bootable), then boot on the DVD/USB and install into your empty hard drive. If something goes wrong, we can help you figure it out.
Don't necessarily get too comfortable with your first Linux, unless you absolutely love it just like it is. We would suggest that you go through the install process 2 or 3 times at least with different versions. It will help you learn the install procedures, and it will expose you to the different "look and feel" that some of the other Linux distros can offer you. It will also help you greatly to evaluate which Linux distros can recognize and use your new hardware.... this is sometimes a problem because manufacturers often do not provide Linux drivers for stuff like sound, wireless networking, etc. Buying the latest-greatest hardware is not always the best idea when you want to run Linux, but you won't know whether your system is compatible or not until you try it.