I need help. A lot of it.

Hello! So recently my Mac laptop of many years has decided she's retiring and I decided I wanted to get a desktop Mac, but with the cost of it being $4500/+ I decided I'll be doing this myself.

I've searched high and low both here and on the internets, I know we don't believe in the UniBeast/MultiBeast and so I've ignored all that but y'all I'm truly struggling understanding anything at all in regards to all this.

I know it's probably not welcomed, but I'll try asking either way, but could someone help me through the entire process?

Currently trying to Hackintosh a Dell OptiPlex 7040. A Dell motherboard, with i7 6700, and my GPU is AMD Radeon HD 6450 (which I haven't been able to figure out if it's supported or not? Because the internet is confusing????)

Thanks in advance!