A lot depends on if you're going to put it together yourself or buy new. If you have stuff you're going to keep ( KB, monitor, etc ), or starting fresh and need it all. Did you want top of the line ? Mid-range ?
Then you come to budget.. Full Tilt Crazy ( no limit ), Moderate ( $1500-2000 ), or Cheap ( under $1000 )...
You can just buy the "box" ( no monitor/KB/Mouse ) with good internals for around $1500.. That's a good processor, current video card, 32 gig memory, and a M2 SSD. If you can scavenge the case/PS/CD/DVD off your old system it gets cheaper by a couple of hundred. Build it yourself and get a very nice system, but you won't save much. Quality will be higher ( IMO ) since you won't have to wonder what corners the builder/manufacturer cut to keep the cost down.
For a VR rig, I would suggest at a minimum :
1 - 6 core/12 thread processor and supporting MB. AMD or Intel.. AMD will get you PCIe-4.. but we don't have much that needs it right now. Reports I've read show it doesn't really add much even if your video card supports it. But you'd be future proofed. Your call.
2 - 32 gigs of memory, and the fastest the new motherboard supports. Period. Full stop. Do it once. And fill all the slots ! IE : If you have 4 slots, get 4 8-gig sticks and not 2 16-gig sticks. You get faster access if it's spread across the entire bank.
3 - Solid state drive, M2. The bigger the better, up to a terrabyte. The bigger drives are faster because they stripe the data across more chips. The sweet spot appears to be 1 terrabyte.
4 - Video Card : This is the killer. Video cards make/break VR. You want FAST, you want lots of memory, all the bells and whistles. But a top shelf one will hurt you for more then the cost of the rest of the PC. As an example, if you can find a 3090 it will cost over $1500. I would suggest going one or two steps down from the top-of-the-line. Like an Nvidia 3070/3060ti or AMD RX 6900 XT . Both good cards that will last, and under half what a 3090 will cost you. The bad part is that the video card market is in chaos right now and NVidia is releasing "super" and "TI" variants, and others just with more memory, at a rapid rate. I am sure AMD will follow suit, or just cut prices. Also, scalpers/crypto-miners bought up most available stock.. so good luck finding one. The only real advice is to get a good as you can afford out of what's available. Or wait a few more months for the dust to settle.