I would worry about the PSU (power source). they use cheap parts in those Dells. if the PSU isn't strong enough your GPU might not work, or it could fry the PSU (and that could take out other components, and even possibly catch fire)I saw a bruh on TikTok say “if you want to buy a gaming computer, but you think it’s too expensive, go buy a Dell Optiplex, and throw in a GPU in it. What’s anyone’s thoughts on this? Can I build a gaming computer for $800? If so, can anyone point me in the right direction, or make me a list of what I’ll need?
and like @Orbital-Fetus said, you might not even be able to fit a GPU in there. there would also probably be issues with the airflow
$800 is kinda low, but you could definitely put something together for that price. pcpartpicker.com is a great site to help you pick out parts that are compatible. they also have a "completed builds" section where you can see other people's builds, and sort them by total price
here's a bunch of builds in that price range