Figured could make this a quicktips type of thread to first time builders. Upon building PC's and searching for the ultimate value/performance I've made several discoveries.
Like for example; eBay prebuilts. I've built 3 rigs this year 2 for me one for a friend, all using the Dell XPS pre-built. They have unlocked top end i7's and a minimum of 8gb of ram. There's tons of configuration options available for them. I've seen i5 4460/GTX 960 configured pre built XPS 8700's for under $600 even on Newegg. Anyways, buying one would be a great way to make your entry point from a GPU/CPU perspective. Most buyers have also tested the hell out of these things, so you're buying used parts in the sense that they've all been stress tested and passed while saving a ridiculous amount. I got an insane used Dell for $550 I use for work, got my friend one for $400 I turned into his first gaming rig, then another which I upgraded the GPU in and flipped for profit. XPS models all come with a 450 watt PSU which is good to handle up to a 770, 970, etc. No X80 series cards or higher end AMD's though. Which is probably for the better considering not much room for air flow inside. But right now you could get a Haswell i7, 8gb ram, and a 1060 for around $700. Which people seem to not realize..
Also used GPU's have a good market. You can get a GTX 770 for a little over $100, and it's a 1080p monster even today.