The oldest computer I still have up and running is ZX Spectrum +2A which is a late model, made after Sinclair's computer business was acquired by Amstrad, but it's still pretty nice to have and it's as close to the original as I can get. I was using local Eastern European clone is the 90's - early 00's, equipped with Beta Disk interface / TR-DOS 5.04T
Here are a few pictures of my +2A. It's a 100% compatible with earlier games, but otherwise pretty nice. Even an integrated tape deck (datacorder) still works.
My first computer, apart from a Sinclair programmable calculator, was a Sinclair ZX80. I was fascinated and started learning how to program. I remember reading about the CHR$ instruction and figured out how to get it to write on the screen Hello World one character at a time. I thought I was very clever until I turned over the page of the manual and learnt about strings and found I could do it in one command. Computers were brilliant because they would do exactly what they were told—unlike the kids I was teaching chemistry at the time.
My next computer was a BBC Model B (Much better manual and you could save on 5¼" discs!) I switched to teaching computers and found myself also teaching the staff how to use them. I learned how to network the computers using a 380Z fileserver. I bought a 10MB hard drive thinking "I'll NEVER fill that!"
From the BBC B I went to Acorn Archimedes RISCOS computers - my favourite machines of all time. I still miss their 3 button mouse concept where right clicking had the opposite effect to left clicking.
Sadly Acorn died leaving only it's subsidiary ARM. I moved to PCs.
Started with IBM 1410 Autocoder in 1964, last used Cobol and Paradox. Also P/L1 and a few others, some not major. Most interesting project -converting a Limousine Rental Service quoting system from a TI calculator to an Amstrad PCW using DBase 2! (approx 1984).
In one sense, Acorn won. Updated versions of its CPU, the Acorn RISC Machine or ARM, are used in mobile electronics everywhere. Unfortunately I don't think we ever saw an Archimedes (or even a BBC Micro) "on this side of the pond".
Yes the RISC technology lives on to this very day from the cell phone to the raspberry pi. I believe Russia will be utilizing some ARM technology in its new in-house processors. I hope Russia can make a secure processor so we can get away from GCHQ and NSA spy chips from hell. The Micromen film was fun to watch and brought back fond memories. In my opinion the BBC Micro was trash but the Archimedes was a beast.
If you have high budget, go for i5 or i7 with graphic card (2 cores isn't enough for future); if you have medium budget, go Amd FX series with graphic card; other wise Amd APU with a high performance Ram is a good choice. But I think you should investigate to other part too like power supply, a good power supply save your bill very much (a good power supply can be with you over 10 years); a high grade mother board make your entire system run smooth and effective; a SSHD is good choice for HDD if you don't have a budget for a SSD. Keep balance your PC parts, a high performance Cpu/graphic card only can't bring full potential of your PC, like driving on off road with a F1 car.