Building a PC is relatively simple, However, if you don't know what you're doing then it can be a bit of a hassle trying to find out where the many wires and screws go.
My advice: Go to the internet. Youtube, google, most tech websites have guides on how to put together all your computer parts.
I learned a lot about computer parts and stuff by watching videos from a guy on youtube called Linus. His channel is LinusTechTips. I recommend watching some of his guides as they go step by step and are very easy to understand.
Unfortunately, you might still not know what hardware to get based on his videos. If you want to get the best help you can on these forums then you need to give us more information about what you want from the computer. We need to know criteria such as--
What games you would like to play
The size you would like the computer to be (not as important but it is still nice to know)
$$Price Range$$ This is probably one of the most important things to tell us so we can get you a computer that can do what you want and not send you into an economic depression.
One of the first things you should know about building a gaming PC is that you do not need to spend as much on a processor as you do on a video card. If someone tells you that you absolutely need to get an Intel processor or else your rig is trash, ignore them. They are what we call Intel fanboys. NOw, there are going to be people who say AMD is better than intel at everything, these are the AMD fanboys. However, both companies are definitely the best at what they do. To sum it up, AMD is for a builder on a budget, but can still provide excellent performance. A lot of people say that AMD is more appealing because at an $80-&120 price difference, 10-15 FPS is not that important. Now, if you have the money to spend for an Intel processor, go right ahead.
NOTE: To compare intel vs. AMD look up the AMD FX-8350 vs Intel i5-4670k benchmarks.
Graphics are the heart of the gaming machine. I would recommend buying an AMD processor to save money for a better video card. An AMD FX-6300 will be able to handle almost every game on the market right now unless it is incredibly CPU taxing.
Nvidia vs Radeon Video Cards--
Usually, Radeon cards are cheaper than Nvidia cards. Radeon is the R7-R9 and the HD #### Cards. Nvidia are the GTX ### cards. However, due to bitcoin and other crypto currency miners buying up all the Radeon cards, Nvidia is currently the way to go. For medium gaming, a GTX 750 Ti will do you just fine. I would consider going with a GTX 760 or higher if ou plan on playing BF4 on ultra. But, do some research yourself and come up with your own results.
Mantle: Mantle is a new software technology that is supposed to make games run faster on the Radeon cards. This is something to think about when buying a Radeon or Nvidida card.
Well, that's all I can think of to say right now. I'll edit this post later if I think of anything else to add.
See ya on the forums,
Addo
EDIT: I would highly recommend not buying any pre-builts for gaming because they often spend much more on a processor than a video card. Trust me, you do not need an Intel i7-4960k extreme to run games paired with a GTX 750. Just a thought
Oh yeah, I can also give you an items list if you want me to.