As others have mentioned, prioritize CPU over GPU. A new GPU would be awesome but a used GPU wouldn't be awful, especially if from a previous generation. I'm pretty happy with my 4060, and with my 12900k I'm able to run Val at 300+ fps on a 1440p monitor.
AMD has trended better recently for gaming. I like Intel, but that's only bc thunderbolt which doesn't mean much for most people and they've trended better for single-threaded tasks, which games often aren't. For the layman, all this means is AMD for gaming, Intel for work. This isn't to say either CPU is bad for either, just a bit of an advantage.
NVMe SSD > SATA SSD. Two different flavors of SSD, but I would make sure your primary is an NVMe. SATA would be fine for secondary storage. Make sure whichever you choose for your primary storage, that's it's at the very least 500gb. It's very easy to download random files, the occasional Steam game on sale, Discord, whatever apps and find that it quickly fills a small drive. 1tb would be better but you'll be fine with 500gb. I recommend Samsung or WD for either NVMe or SATA SSDs.
For choosing RAM, just make sure your motherboard is compatible with it.
For choosing a motherboard, you don't need anything crazy expensive with AI overclocking or whatevs. You probably won't be overclocking your PC anyway, so just make sure it has enough USB ports and NVMe slots. If it doesn't have wifi included, it's not hard to add it later for a couple dozen bucks.
Don't neglect cooling. It probably won't matter which fans you buy nearly as much. Noctua is a good one to go with. If you want RGB, a lot of big names have proprietary software that can be hit or miss and is another app to install.
For your CPU cooler, air cooling can achieve the same results as a liquid cooler (Noctua heatsinks are goated), but I like my AIO liquid cooler because it's less noise.
A big part of cases is aesthetics but that's not the only thing. Check out reviews for any cases you have your eye on to make sure it isn't a headache to build in or maintain.
The combination of CPU and GPU will determine the amount of frames you get. The amount of frames you get won't matter if your monitor can only output 60hz. Even if your game is putting out 250fps, you're only effectively seeing 60 fps on a 60hz monitor. If you can snag your dads or a similar one for cheap for now, you'll be fine. I'm worried a budget of $700-1200 will be just enough for the PC and not much left over for a decent monitor depending on what you choose. I'd aim for $250-500, also depending on whether you just want something that gets the job done or if you want a solid viewing experience. The monitor is what you'll be looking at all the time.
I sell/build/troubleshoot these things for a living so I'm more than happy to answer any questions, this is the roughest outline I could give. I'm sure mongu will guide you in the right direction tho :^)
ETA: you might save some money with a prebuilt, I've often run into Lenovo or HP prebuilds using cases or weird OEM motherboards that do annoying OEM things but the rest of the components are the same. iBuyPower and CyberPower are good. NZXT is pricier. Avoid Alienware. Building a PC is much more fun and rewarding though.
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