CPU, CPU, CPU. Some RAM and any gpu really, depending on your resolution.
For cpu, you want more than 4 cores and the highest single core performance you can find.
An important thing to know: the more expensive CPUs within a generation with more cores barely give you any performance for our most used simracing titles.
You get a bit more performance due to the higher clockspeeds and a slightly bigger cache.
But it's absolutely NOT proportional to the costs!
So the sweetspot since a few years are the 6 core CPUs with higher performance.
AMD 3600 or 5600x. 5600x is a class ahead. Quite a massive difference to the 3600.
1600 and 2600 have not enough single core performance for intense simracing.
With Intel, the 7xxx series was the last one with only 4 cores.
8th gen to 10th gen was basically identical in single core performance, the 11th gen was a new architecture but has some issues with some games and basically should be avoided.
12th gen is expensive and superb.
In short, if Intel, either get a 8600k/9600k/10600k/12600k.
My recommendation would be an amd 5600x though.
It's on par with the 11600k if the Intel works and is a lot better if the Intel doesn't work.
I've put it into 3 builds for friends and they are all very cool, efficient, massive in performance!
Slap some cheap DDR4 3200 or 3600 CL16 at it and be happy. Depending on current price fluctuations, the sweetspot varies.
With motherboards: the cheapest, good motherboards with lots of usb for us simracers are:
Gigabyte gaming x for Intel and for the 5600x I'd recommend the:
Msi mpg B550 gaming plus.
Here in Germany that would be 250€ for the 5600x, 50-65€ for 16gb ram, 110€ for the motherboard.
Use your current gpu, case etc.
A cooler is bundled with the cpu and that's OK.. If you want a silent and a lot better cooler, get the be quiet pure rock 2.
Lots of tutorials out there how to build a pc if you never did it.
Basically all things only fit where they should.
Mount the motherboard first (with ALL screwholes supported) and then you can put pressure on it when putting in the ram sticks, gpu and cables.
What resolution/monitor do you use currently and what's your current cpu and gpu?
I sadly forgot, sorry