As most PC Gamers will say,
Build your own PC.
What I mean by that is not to get all the materials and shit and start making your own motherboard
You can look up on the internet for all types of motherboards, graphic cards, GPUs, processors, cooling fans.
Whilst I'd love to help I have shit desktop of my own (pre-made bundle - despite being able to run all of GMODs gamemodes at a steady 20fps or higher) I also have football training, I'm sure some people here are more experienced at helping you though