Looking for PC Setup Tips?

Go with used lga 1366 Xeon CPUs. E5-2670 in lga 2011 is also a good choice but it has eight cores and games usually use 4 of them.
Check Passmark.com, anandtech.com, etc. about price/performance.
Don't be afraid to buy used or refurbished parts on eBay. They are simply cheap and good. If you receive one that is defective, you can always return it back to seller.
$1200 should be a water cooled build, but you can use air cooling and throw the budget on you system power if you don't bother overclocking.
Use the case of known brands. Last time I bought a case that is said to support 240mm radiator, which does not.
If you like lighting, Definitely buy NZXT HUE+ lighting kit. It is worth the money.
Don't buy overpriced parts for you theme build. Simply buy some plasti spray paints to paint case and you heatsink. It is a lot more fun and what you only need are card boxes.