The Meaning of Life, the Universe, and Everything.
I would recommend custom building a PC, probably would be cheaper then buying a pre-build one. Doing this does require knowing how to build a PC and
what parts would be good, like to record both minecraft and CSGO, you wouldn't need a super powerful graphics card, just don't have a potato.
Also video editing programs take a lot of CPU power, but an average one works just as fine, its just not super-speed fast.
Buying a pre-build PC usually costs more, but you may be able to find one at a good price.
I wouldn't be able to help you with building a PC, i'm not super experienced with it, but i bet you could find many people who are with a quick google search and they would probably happy to help with that.
Whatever you decide to do, just make sure you don't get ripped off. Many people try to sell PC's that are worth much less then they say. (This mostly happens with private sellers on sites like craigslist, also don't trust to many super amazing deals on eBay either)
I've tested recording on my PC and it was fine. My PC was $800 CAD so if you live in the U.S.A you can get a similar setup for around $650 dollars
If your wondering my PC has a nvidia 1050 graphics card, an Intel core-15 2400 quad core processor, and 8G of ram. If you are going to record i would recommend at least a nvidia 1050ti or a 1070, and while 9 gigabytes of ram isn't completely necessary, if you play with mods it will help a lot.
(I dont know my specs any more specific then this, please don't ask)
Checking the price of components online on official websites before buying in stores can give you a baseline of how much you are being ripped off.
Shopping online is cheaper most of the time, but sometimes its still overpriced or it can be a scam
In short, just research the parts you want, and make sure you know what your buying and its price (Don't get scammed)
The crypo currency thing (like bit-coin) is causing many people to buy tons of graphics cards, and the price of graphics cards is high right now. You might want to wait for prices to go down, but that could take a long time. Maybe you'll be lucky and it prices will drop soon.
Also make sure parts are compatible if you choose to custom build a PC, and you'll need to install drivers if the PC isn't already pre-build or setup.
If anybody more knowledgeable on the topic of PC's sees any errors, please correct them.
Some other things you might decide to do is use a B350 motherboard (which would allow for overclocking), or remove the SSD (although you would suffer much slower boot times, but once you use an SSD, you won't ever want to go back.)
Also, once you've built this PC, I'd stick to using AMD ReLive, not only does it come with your GPU, but it does not impact performance very much while still delivering very good quality recordings. If you decide to buy a NVIDIA GPU later down the road, NVIDIA Shadowplay is NVIDIA's version of ReLive.