It's hard to answer this question since there is little info on the game's requirements right now. Judging by the graphics we've seen so far, it surely won't require a huge gaming power beast (which thus makes it accessible to more players).
Since you're not familiar with building computers and stuff, the first thing I suggest is getting familiar with it! I'd start off with a well known website, like
Tom's Hardware, and look at the "Build your own" section to see what you can get in your price range. Then, Google a little, ask some questions, read more stuff, look at specification sheets, tips on assembling a PC, ask more questions, etc. In the end you have to be confident you made the right choice. Also, when using internet as a resource, do not believe anything right when you read it (and that counts for what I'm going to suggest below): if someone on a forum says X is better than Y or that you should do Z, then hop on Google and look more into it.
Alright so, for the computer itself, I'd start out deciding if I want an AMD or Intel processor. Games nowadays still do not make much use out of multiple cores, so some people prefer going for a faster dual core than a quad core for example. To decide on that, I'd consider what other stuff you'll be doing with your computer. If you're planning on doing some heavy compiling, video editing and similar tasks, then having more cores available will help you. If you plan on gaming, browsing and watching videos, then it probably won't matter that much in the end.
Once you kind of know what processor you want, choose a motherboard with the right socket for it. That's the part I dislike the most since the motherboard is very important but hard to sift through all the features and trying to figure out if you're going overkill or not can be difficult.
Familiarize yourself with the motherboard's specifications and go hunt for some RAM. Check the max speed that your board can handle and choose accordingly. You might have to read quite a few reviews here to figure out which brands/series to avoid. As for the amount of RAM, 12-16 GB is waaaaaaaaaay overkill in my opinion. Unless you are going for some heavy video/audio/photoshop work, having more than 4-6GB won't help you much. I've been running with 8GB for a year now and I still consider it overkill. On the other hand, RAM is kind of cheap and going 6-8GB with dual/triple channel isn't that expensive.
Once that's done, think about your graphics cards. ATI or Nvidia? They both have their ups and downs and every series had their moment of glory. This is probably the most touchy subject when it comes to user reviews, so be careful. Check what features the cards offer (e.g. integrated PhysX in Nvidia cards) and benchmarks to see what's the competitor's equivalent card and compare prices.
By now you should know how much power your PC is going to need so start looking into power supply units. Then again, it's a little touchy: it's easy to go overboard with the wattage but picking a cheap PSU won't set you on the right road. Don't just look for power, look for efficiency as well.
Now what's left is getting your hard drive(s) and a case. I don't have time to go into that right know but it should be pretty straightforward!
Hope that helps! And remember, don't trust anyone!
