Do you know what your purpose is going to be for this? is it just for daily use or is it for your CAD program? Do you know the minimum specs for your CAD program (include CPU, GPU/VRAM, certified GPU or notand RAM requirements) that would help a lot with the roadmap to building a new computer and budget feasibility. My first thoughts are you should probably go with an Intel processor (because of the high core counts). The constraint is going to be your $1500 cap, right now RAM prices are not your friend.
I’ll wait to see your answer and see if together we can put something together for you. In the meantime here’s some videos for you to watch and see if you think you want to build your own or buy a prebuilt.