For that budget you can build a PC that will do 1440p 144hz today, no problem, which will be able to give you 60+fps AAA for the next ~4 years. (Especially as frame gen tech like DLSS and FSR get added to games)
1440p 60fps for today’s games you can do for half your budget.
For a tower, you need 7 components:
mobo, ~$100 ($150 probably more realistic)
CPU, $100 ($150 probably more realistic)
ram, ~$100
case, ~$100
PSU, ~$100
storage, ~$100 (you can get a Crucial P3 pcie3 2T for less than this right now).
video card, anywhere from $200 ~ $1400. Pick your poison.
Excluding the video card, that’s 6 components for the $600 ~ $700 range. If you go thrifty and watch out for deals you can get sub $100 on good quality PSU, case, and RAM which basically puts you right at $600 for a full PC in which you can put any kind of video card you want in depending on budget (however I would say once you start getting into the rtx4080 or 7900xt and above territory you might want to consider upgrading the CPU as well.). Additional peripherals like a monitor will cut into this remaining video card budget, but I highly recommend a good gsync monitor as it basically turns any 80 FPS gaming into a 120+ fps experience.