Office chairs around 400 to 800$. It's god damn pricey but an absolute life change if you spend a ton of time at your computer. Are so much better for your back and butt and is worth the money 10x over considering the pain it'll save you.
If you can't fork up the cash, do a ton of research, learn a lot about specific models and then on Facebook marketplace (or any other local marketplace) search up "office chair". Oftentimes people sell premium office chairs without ever knowing, this way you can snag some for ridiculously cheap. Usually around 100-200$ but if you are lucky 10-30$.
Also avoid "gaming" chairs. Like most gaming related stuff, they're awful and you're just paying for the edgy look. I had multiple of these and each one was an ergonomic catastrophe, even expensive ones.
The suffix "gaming" implies bright colors, low quality, and a higher price tag. It's right next to "premium" for identifying garbage products.
Also, I've had so many cheap chairs in my life that just failed. The "leather" peels, the gas lift breaks, or the seat cushion wears out and causes pain and discomfort.
That said, you can buy new gas lifts to fix a sinking chair very cheap and buy additional cushions to reduce pressure. If you can't afford a good chair, don't keep buying new bad ones!
Yeah, personally I find that everyone can afford luxury if they are clever enough. So either finding a used one cheap, fixing an old one for cheap or modifying another one. It's what I've done for all of my knives and tools and they work like a charm without the price tag.
Most 'gaming' chairs are trash material covering shipping foam - garbage.
There are exceptions though. A couple years ago I bought the least gaming looking full leather seat from noble, same foam as good car seats, leather very good, and got it on sale for a silly price. 2 years later it still looks the same as day 1 and the foam hasn't started to deform yet, I work in it all day.
All my back pain from previous shit chairs was gone in a week too. After that I'd have been happy to pay double.
As in most markets, there are always diamonds in the rough, the hardest part is just identifying them.