Before I lay out my thought process behind each part, there are at minimum seven parts you’ll need to build a gaming PC.
Graphics card, or GPU: Arguably the most important component in a gaming rig, the GPU (graphics processing unit) renders images from your PC and puts them on your monitor. More powerful GPUs facilitate better in-game graphics and settings.
Processor, or CPU: More so than any other component, the CPU (central processing unit) is what makes your computer run. The CPU routes instructions from one system in your computer to another. The better the processor, the faster it can transmit information for both software and hardware functions.
Motherboard: The motherboard is where all the hardware in your computer lives. The most important thing about a motherboard is its compatibility with the parts you choose, but motherboards can also have integrated graphics cards, Wi-Fi systems and more.
Memory, or RAM: RAM (random access memory) determines how much data your computer can process at any given moment. To oversimplify things considerably, RAM is where your computer stores information it needs to access right away. The more RAM you have, the more efficiently your computer can process lots of information — helpful for productivity; essential for games.
Storage, or SSD/HDD: PC storage essentially comes in two flavours: Solid state drives (SSDs) and hard disk drives (HDDs). Either way, it’s where your files live when they’re not in use. Bigger drives mean more storage space, which means more room for files, games, media and so forth.
Power supply: Possibly the least interesting and most vital piece of the PC puzzle, the power supply is exactly what it sounds like: It gets electricity from an outlet to individual systems in your computer. Picking the right one can be tricky, but once you do, you’ll probably never need to think about it again. This is not something to save on, as a good PSU will also have protection in case of a power surge/failure – this could cost you your whole PC if it fails!
Case: Your computer case is, for the most part, an aesthetic choice, although some models include fans for additional cooling. While it’s possible to do an “open-air” build, a case is probably a better choice for keeping dust out and components sheltered.
RGB: It’s been proven many times that having loads of RBG strips and fans give you a huge performance boost in everything you do on your gaming PC. OK maybe not, but it does look really cool while also keeping your components cool! That’s a win-win!
Anything else, such as additional cooling systems or secondary hard drives, are nice to have, but not strictly necessary. These are the parts you need to go from a pile of hardware to a functioning PC.