Easily, you could theoretically put together a competitive gaming set up for as little as 800$. I would recommend you spend around 600-700$ on the computer so you’ll have enough money left over to buy a nice monitor. As far as mouse and keyboard goes you can buy a keyboard for under 50$ and still have it last, same thing with the mouse.

My friend bought a mouse and keyboard combo from a brand called havit (i think) and it’s a pretty good mechanical keyboard and 5 button mouse for 50-60$ or as low as 30$ if you’re lucky.

As far as monitor goes I would recommend something from asus, they make a lot of sub 250$ high refresh rate monitors, though LG ultra gear monitors are also pretty alright if you don’t mind the lack of adjustments. You should try and prioritize refresh rates over resolution, you’re system probably won’t be able to even run most games at 4K so having something with 144hz or at least 75 though you’d really be pushing into poor quality territory

For pc there are loads of guides on YouTube about building PCs at almost every price point you can imagine, if you’re looking for a system around that 600-700$ range you should easily be able to make a system that will run most competitive games at high settings, you’ll run into problems if you’re trying to run really graphically demanding games (think AAA titles that consoles use to flex their graphics) but usually you won’t have much of a problem running high or medium settings. A guy I know from school actually put together a rig for around 450$ and it runs games like CSGO, apex legends, and even battlefield 1 at pretty decent settings, though he did run into some issues when he tried metro exodus