Suggestion on what to buy and where to buy PC

Hello there!
I am interested to learn about Magic Micro Computers. I am considering assembling a computer and I’m in the process of researching for the ideal computer and for the places where I could find and buy it.
For the computer I will be assembling, I need to have applications relevant to engineering such as AutoCAD, MathCAD, and OrCAD.
As such, I want to build a computer that is personal but can perform optimum calculations. I don’t need much of high-definition graphics since I’m not into gaming anyway.
I was considering AMD 64 but I’m looking for other options.
I hope you can give me suggestions on what to buy and where.
I would appreciate your ideas.
Thank you very much!
