Buying in on a PC isn't such a bad idea right now - mainly because with all the new gen stuff coming out (particularly from AMD - but I doubt Nvidia/intel are that far behind) a lot of large retailers and warehouses are clearing stock and I imagine sales will come up fairly frequently for yesterday's news.
If you're not intending to be a big time streamer or do tons of video editing for hours upon hours, that would be the market I'd look to get in on - regardless of whether it's AMD/Intel Nvidia/ATI - if money is a huge concern you have to decide at which you're going to cut off spending on each individual part and what your budget over all is.
You'll likely, depending on sales, get a better deal for AMD products because they're typically cheaper for roughly equivalent specs - but you never know sometimes you can snatch things up for maybe 20-50$ more, and you have to decide if that's something you're willing to do.
Building your own PC is basically as easy as putting legos together - there's nothing to panic about unless you're very accident prone and like to spill water all over yourself. .
The best advice I can give you is:
INCLUDE warranties into your budget. If something is 10$ more expensive but offers 1-2 extra years of warranty, that's not a bad investment. Look at the different vendors (newegg, amazon, bestbuy, ebay, tiger direct, direct from manufacturer, etc)and see what sort of warranty policy they have - some stores offer you their own warranty ON TOP of the part's own warranty, and that is definitely something to keep in mind. Typically things don't break down that fast if you pay for quality hardware, but you just never know when something freaky may happen, or a design flaw nobody saw coming pops up.
Think about routine maintenance. Is this case/hardware going to be easy for you to maintain (this is a big one for people who are first getting into things like liquid cooling, or want to buy a fancy case, or do a funky HDD set up).
Make sure the manufacturer is a reputable and established company - there are lots of new hardware companies cropping up all the time, and they are relatively short lived sometimes, and that can leave you in the lurch if you take a risk on a new manufacturer. If you choose to go this route, I would strongly suggest investigating their customer service practices and perhaps look for that kind of content in reviews - the first case I bought came with the wells for the MOBO screws slightly out of alignment, and when I tried to get in touch with the manufacturer, all I kept getting were messages in Cantonese - despite them having a website that was in English, and the company died only a few months later, and I was left with very big piece of scrap metal. But it turned out OK because I just made new holes for myself - guess it should've said some assembly required.
Spending big on CPU and skimping on GPU is a good idea if you're short on money.
Depending on what GPU you have right now, you could even just continue using the one you have and throw even more money into your CPU. The reason for this is that it's often impossible to upgrade your CPU - socket types change frequently enough that if you don't plan to be able to drop another 200-500$ on another CPU in the next 2-3 years, you're going to want to spend more money on a CPU because that *will be* your CPU for the life of the machine most likely. Graphics cards however are a different story. Their socket type as it were hasn't changed appreciably in the last 10+ years (since we stopped using AGP ports) and likely won't be changing in a big way any time soon. Even if you have a PCIe 2.0 card and a 3.0 PCIe slot, you'll still have a functional GPU. Then 2-3 years from now you can just buy a new GPU as an upgrade.
You can do the same for RAM - so long as its compatible with your chosen CPU, and just upgrade to more later on in life (it's cheap anyways, and will only get cheaper). You could also try to salvage your power supply as long as it isn't super dirty, works correctly, and has the required amount of wattage for your build. That's a few hundo in savings at least. Maybe you'll have to buy more later, but it can put off the cost until you're able to save up more.