I would have to agree with chunderburger, but with a bit of 'what's your budget' and 'how patient are you ?' thrown in for good measure
As a hobbyist, my PC upgrades are down to when I can afford them or when something packs up and has to be replaced. I do allow myself a two PC setup though. I have one principally for internet use and a second one for Lightwave and similar product use. In years gone by, I used to build my own PCs but in recent times I have gone with refurbished off the shelf ones as they worked out cheaper. Back in 2019, my setup was a Lenovo ThinkStation S20 E5420 CPU 12GB DDR3 RAM 1050ti 4GB for internet and a Lenovo C20 2 x E5620 CPUs 24GB DDR3 RAM Quadro K4000 3GB GPU for Lightwave.
My internet PC started to show signs of age with boot problems and RAM failures, so I hunted around for a replacement on a tiny budget of £300. In May 2019, I lucked into a refurbished Dell Precision 5810 off eBay for £275. It included: Xeon 1620v3 3.5GHz CPU,16GB DDR4 Ram, Quadro M4000 8GB, 1TB HDD. At the time, I looked on it as buying the M4000 with a free PC thrown in as a bonus. The 1050ti went in this 'new' PC and my Lightwave PC got the M4000.
Early last year, my LW PC started to have memory problems so I tracked down a replacement on eBay. I got lucky again and this time picked up a refurbished Dell Precision 7810 2 x Xeon E5-2680 V3 CPUs, 64GB DDR4 RAM and a 512GB SSD for £420. Both Dells came with 825W PSUs too so had scope for expansion. Soon after that, I stumbled across a 2080 RTX GPU in the Amazon Warehouse section for £445 (about £200 below the regular list price at the time), so snapped it up. Definitely my best buy last year given the silly prices currently being asked for similar kit.
So now I have two decent Dells as my main Internet and LW machines with the Lenovo C20 as an internet backup that can also run LW if need be.
The point of all this rambling is that there are lots of options for getting decent PC upgrades if you are on a limited budget but have patience and are willing to shop around and compromise a little