Build one.
Even if you know nothing about building one, doing your research and finally sitting down and putting a comp together is fulfilling as stuff.
I also know nothing about which components are considered good and which aren't, and the reason I'm looking for a custom made rig is I really don't want to build one of my own as of late. I know how to put one together, but it's not convenient for me, and I am willing to pay the extra dollar to have someone else do it, and have it covered in warranties.
usually you would hope for near 60fps on a computer. since all monitors will support at least that much. and its been the low standard for over a decade anyway.
My first computer could barely run RCT2 and a few hunting games I had. Like, maybe 10-15 FPS max.
My second could run Runescape at the same, and Blockland was an absolute nightmare with only 10k bricks or more. The last half of me owning this computer, I was also well into playing Playstation and my Xbox, since they were the only things powerful enough to play games nicely.
Now that my current PC is getting old, there isn't really much it can run at acceptable framerates without having everything dropped to low. Not that I mind.
Either way, I'm used to 30fps. I know 60 is the standard that everyone tries to shoot for at least, but I can still find a game perfectly playable at anything above 25.