Based on current timeline, not an ideal time if you are going for a new build since AMD have quite a bit of new stuff lineup for release till end of the year.
But should you need one right now think the specs below should suffice.
Price hard to gauge as you are buying everything at the store which will net you a discount and you have to personally negotiate for it.
CPU: Ryzen 5 3600, 6 core 12 threads ($200 more to get Ryzen 7 3700x which will be 8 core 16 thread).
Ram: 2 x 8GB 3600mhz DDR4 Ram, CL16 or CL18 is fine. ($107~$170)
Motherboard: MSI B450 Mortar Max, Asrock Steel Legend B450M ($150~$190)
B550 due on 16 June, can opt for those unless you need it before that date.
Graphic Card: Any brand of Nvidia RTX 2060 Super is fine. ($570~$700)
RTX 3000 series are coming too.
SSD: NVME or Sata both works. For NVME can consider WD Black. Amazon SG has WD Black NVME at 1Tb for $210, significantly cheaper than SLS prices of $300+.
WD Blue 550 was recently released, an upgraded version of the blue series. Slower than black and slightly lower price.
PSU: Superflower Leaderex III, Seasonic Focus GX, Evga Nova 3
650W or 750W are fine up to you to buy more for leeway or settle for lesser.
($140~$175)
CPU Cooler: Coolermaster 212 Series ($35~$70)
Case: Whichever one you like as the boards chosen was matx, smaller than atx so it will fit normal atx case too.
So you have 2k spent on the desktop which you shouldn't have to upgrade for at least 3 years. Graphic card chosen based on 1440p settings. If you want to go higher you need to buy 2070 or 2080 and likewise monitor pricing will follow suit since you be going into 4K visual range.
For monitor best to go store to see while you pickup the rest of items.
Well, all hope is not lost if you want to build a pc now, just that we can minimise your loss when u do a minor upgrade.
I'd say skimp on the cpu and graphic card and build a solid backbone set up.
CPU: 3600 is fine and your intention would be to sell it away when zen 3 comes. If you can buy it cheap for second hand (230-240) it would be great. Next time when you sell, perhaps it can fetch 180-220 (small loss for 6 mths of usage)
Mobo: Get a x570 board with wifi if u require. Bios will probbaly be able to be flashed to support zen 3
gpu: get a cheap second hand rtx 2080ti. There are people selling for 1200-1300. Next time you can resell it for a small loss and get the flagship 3800 or 3800ti.
Ram: 32gb, at least 3600 mhz
cooler: use the stock cooler for now, and consider fancy ones after u swap out cpu
SSD: even 1tb is not enough to install games on the maid drive. If you can. get a 2tb nvme drive or 1tb main and cheap 2tb sata drives (all SSD pls)
psu: please dont get strange things like superflower or fsp. Get A rated PSU like seasonic focus plus/prime, evga g3/g+. You dont want to touch ur psu for a decade, so get a good one
these parts shdnt cost u more than 3k - leaving the balance 1000 (and extra top up) to replace parts 6 mths later.