How to build a gaming Pc that is amazing in performance and very affordable?

How to build a gaming Pc that is amazing in performance and very affordable?
Added (1). Edit
Update: I've been looking into building a gaming PC, but I really don't have a lot of knowledge on parts or how to build one (although I am doing a lot of research). I'd like to hear some suggestions as to what parts are best for gaming, and how affordable it is to buy those parts and build everything:)
I'm currently using this website to help me decide: http://ca.pcpartpicker.com
My budget is capped to $800 but I'm keeping an open mind.
Added (2). Also, I would ideally want my PC to run League of Legends, Minecraft and other games on Steam if anyone was wondering

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