Planning on purchasing a gaming PC, need help!

*I copy/pasted this post from another because a guy reocmmended I ask in this community! Sorry if you're re-seeing this!

All my life I have solely used Mac, however, having an 8GB RAM iMac and trying to run the likes of Baldur's Gate 3 doesn't work as well as you'd think (or maybe, works as well as you would think, given how Mac's just aren't suited for gaming lol), and so I've been debating (for a while now), whether or not to purchase a gaming PC?

Now, I know practically nothing when it comes to processors, RAM, intel, specs, and whatever-the-hell-else!!, so I don't even know where to start here. All I know is that I want to run the likes of Baldur's Gate 3, and other games not available on Mac (such as Elden ring, etc) smoothly and without it crashing nonstop -- or even just not opening (cough cough BG3 cough cough). I'm honestly just sick of spending money on these games and not even being able to play/enjoy them lol..

Now, I also know that wifi speed and such is important when running these big games, however we just got new wifi and I think (despite not being knowledgeable on what's good/isn't, I mean, if stuff opens smoothy then it's fine right?) our wifi is fast. I googled a wifi speed test and got 115.4mbps download, and 21.5 mbps upload, if that helps at all LOL. Also, we do live rural Scotland, so wifi has just always been kinda an issue.

All in all, any tips would be great! Would buying a pre-made pc be better than a custom one, or vice versa? On average, what would the cost be for a good pc (I'm planning on selling the iMac and then saving the rest of the way to purchase it)? also stuff like monitors, too! Because you can't have a pc without a monitor right lol