Spoiler: Definitely an experience you would want to try before it's too late! I would agree with you, however, that buying a pre-built is not always as bad as everyone makes it out to be though. You just need to be smart about it.
Just built this bad boy for an engineer here at work. https://pcpartpicker.com/list/hyG4tJ Replace the GPU with a gaming GPU and get a smaller M.2 SSD to maintain your budget. This one will last you a while. Fuck, GPU's are expensive. RIP