[Build Help] Minimum, but scalable pc build.

I'm trying to build a pc with the minimum parts required. I need a pc now. My budget is less than £500. I want to add the graphics card, cooling system, optical drive etc in the future if possible. I need your help in finding a cheap power supply unit and a case that will allow me to expand into a high end gaming rig.

EDIT: I need a basic home computer for everyday use. Microsoft Office mainly, nothing heavy. I was saving money to build a gaming rig, I had already picked this CPU and MOBO, but my laptop :(

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