the strategy i used when i was picking out parts for my computer was to go to a site that lets you customize a gaming rig (i used origin), pick out the parts you want, and then go to a site like pcpartpicker and select all of those parts. it'll come out way cheaper than what was listed on the first site, and you'll probably end up with more wiggle room to get better parts.
i.e. when i built my 2k rig, i started my list with the near bare minimums from originpc, recreated the list on pcpartpicker, and found i was able to afford another hard drive, 16gb of ram (as opposed to 8), a gtx 980, etc etc
you can also check out logicalincrements or do some searching about for "$500 gaming computer" or w/e
building the computer itself isn't really difficult, it just takes a while and it helps if you look up some guides (i wouldn't have known to clean off the heatsink base with rubbing alcohol before applying thermal paste if i hadn't looked it up). do your research, take your time, and be careful and everything should go fine.
in the end, the extra work is well worth it because you get way more bang for your buck (plus people tend to be really impressed when you tell them you put your computer together yourself lol)
