I’m going to spare you from reading a bunch of crap and just get straight to the point. You need at least 8 gigabytes of RAM on a gaming PC in 2019 if you want to play modern games. More RAM will obviously help, but any less than 8 GB is going to be a bad experience.
Why Is 8GB the Minimum Amount of RAM for Gaming?
Today, most games recommend at least 8 GB of RAM. Only very low demanding games will run well on less than 8 GB of RAM. Fortunately, at a time when $400 laptops come with 8 GB of memory, it’s not exactly hard to get 8 GB. The typical 8 GB single channel 2400 MHz DDR4 RAM module costs around $50-60. Two sticks of 4 GB will cost slightly more because there are now two physical modules, but dual channel memory allows your system to be a little faster.
16 is better than 8
If you are purely using your computer for gaming and literally nothing else (no browsers, no streaming, no editing software, no background programs), you won’t notice any difference in gaming performance between 8 GB of RAM and 16 GB.
However, I’m pretty sure you browse the web, and a few Chrome tabs can easily hog up 2-3 GB of RAM. Add on the ~3 GB of RAM that is being used by Windows 10 and you don’t have much memory headroom for your games. When you RAM capacity is reached, parts of your storage drive (hopefully SSD) are temporarily used as DRAM and even the fastest NVMe M.2 is very very slow as RAM.
This is why almost everyone recommends 16 GB of RAM for new gaming systems in 2019. With 16 GB of RAM, a smaller proportion of your memory is effectively hoarded by the bloated Windows 10 OS and there is enough memory for background programs to work with while your gaming. You won’t need to close your browser tabs to game if you have 16 GB of RAM unless you have like 100 loaded tabs.
The bottom line: If you’re going to spend more than ~$750 on your computer, get a 2×8 RAM kit. It really does help.
What about 32 or 64 GB of RAM?
For most regular gamers that don’t run any intensive background programs, 16 GB of RAM is the sweet spot for the foreseeable future.
However, if you do professional tasks like video editing, computer simulations, CAD, or any memory hungry task on your computer, 16 or even 32 gigs of RAM might not be enough. You will also need a beefy CPU and GPU as well (An APU won’t cut it). You may even want to overclock your GPU as well.
You may also want to get a high end processor/motherboard (AMD Threadripper/TR4 or Intel i9/X299) so you can take advantage of quad-channel memory if you need 32 or more gigs of RAM.
However, if you play a game like Cities:Skylines with a Steam workshop full of user generated content, you might need more than even 16 GB of RAM. You can benchmark your current RAM performance as well.
How Many Modules of RAM do I need?
Basically every single motherboard today supports dual channel memory, regardless of whether it has two or four RAM slots. If you use all four RAM slots, your memory bandwidth will increase, but your latency will increase and two-slot dual channel ends up being slightly better.
High end X299 and X399 motherboards do support quad-channel memory, but that is out of reach for 95% of consumers. You should make sure all your hardware is compatible though.
So for the most part, using a two piece RAM kit is the optimal configuration. You get the benefits of dual channel memory without the increased latency from using more than two RAM sticks.
Using just one RAM stick running on a single channel is not actually bad, and your computer won’t actually run 50% slower, but there is a small 5-10% measurable decrease in overall PC performance going from dual channel to single channel RAM.