Well, any store branded thing is probably your best bet.
A store built system is fine.
If you can't afford all that, buy a case, supply and upgrade kit.
No kits I have seen have a case and supply but get a good case, a 550 watt supply or 600 which is all you really need in most situation, 450 units are fine but are only for stock stuff.
It depends on your budget.
Intel 9th 10th or 11th generation are the top intels but as I said depends what you can afford.
7th and 8th are ok and 6th can still be good.
A processer upgrade kit will have a board, cpu and some ram.
A storage upgrade kit will have a couple drives.
If you don't want to fart with that, I'd get an upgrade box, thats a basic box with no os.
Those usually come with a 1-2tb hard drive a board and processer and 8gb ram and thats it.
You could get extras like an os or a ssd.
redmondpie.com have offers for cheap windows and office and while I have only ever used their office offers they have worked.
Then again, if you are custom building your box, you get oem and builder rates and some stores do promotions and gift boxes.
Mostly these contain games and a load of other things we can't use but they can contain hardware and random stuff.
At any rate if you get something you can't use, you can sell it back on ebay and get some cash back from your purchice which means more stuff.
16gb ram to 32gb if you can afford more than 16 will help and anything over that is what ever you want.
I have seen a lot of units able to take 64gb, that being 2 32 gb ram sticks.
Some can take 128gb ram or higher but after 16 32gb all at once can cost a little bit and after that it gets silly.
If you are never going to play anything with sightlings or don't have cash to spare I wouldn't graphics cards over 1gb cost a load.
Of course if you have 3-400 bucks you can get one.
Amd is good and nvidia aparently has jaws issues.
You probably don't need any more than 4gb graphics unless you really plan for the biig leegs.
Drive storage, well a 128gb ssd and 1tb or 2tb or higher hdd will handle for most users.
However you can always get more, 256gb or 512 maximum for the system.
If you think you can get another 1-2 tb for things and maybe another extra drive go ahead but at least here in new zealand 1-2tb ssd costs as much as 4tb of hdd storage so it may be worth looking at your options.
An internal or external usb 3.1 sd reader could be a good extra, and a disk drive, dvd writer or at least dvd reader and cd writer or just reader or reasonable speed.
Its your choice to include usb c support but it depends on devices you have.
Over that if you are away from the wires then wireless would be good something with at least ac 1200 or 1.2gbps will probably do but whatever you can afford.
Over that if you still have cash, then a good soundcard, the shops have a few but if you are into music, dancingdots.com has a load of specialty cards if you are interested.
Most are usb but creative still has the audygy fx and that may work.
Cpu wize, amd ryzen 5 or 7 are the gold standards of gaming there even is a 9 now.
If you don't have that sort of cash, I'd go for a standard top range epending on price i5, r5 or i7 and or r7 respectively.
The amd systems have drives twice a month, and release all their betas for free publically.
Intel update 2-3 times a year so whatever floats your boat.
I am not sure about normal stuff but hp systems do have virtual machine capability and the prodesk I was installing for a client, had a door with a cardoor like handle on it for easy modding of the system.
So if you are not sure what you want, get an hp pro desk, then get bits, pull off the side and go to town.
The only issue is you will need sighted help to set the complex bios interface manager system.
You do not want it to come on or shut down at a certain time which I had to do because it was configured to do that when I had the system first.
Depending on space you may want a miniture desktop which is all nice and small and has everything to.
The advantage with a pro desk is its like a laptop in a desktop shell.