There are a few things you're going to need. A CPU, GPU, PSU, RAM, storage, a case, and a motherboard.
CPU: Right now I have the AMD FX-8350 Eight-Core Processor, which runs at about 4.0 GHZ. Some people say to only go with Intel, but I think they give only slightly better performance at a much higher cost. Just my opinion: go with AMD.
GPU: Can't help that much. I need to upgrade mine too. My only advice I can give here is go with ATI over nVidia. It's the same with the Intel/AMD thing, nVidia is going to charge much more for only slightly better performance.
PSU: Not much goes into a power supply. I prefer corsair, just because of the quality, but as long as you get about 500 to 750 watts (depending on the GPU you buy)
RAM: Again, not much here. Aim for 16GB of RAM, but RAM can be expensive, so 8GB is fine too. PNY and Corsair Vengeance are great.
Storage: Go with SSD. Times are changing, and 500GB to 1TB of good, SSD storage is going to last longer. SSD may be a little more expensive and a little harder to install, but you won't have to upgrade for awhile.
Motherboard: ASUS and Gigabyte are the best brands. Find one with 4 RAM Slots and at least 1 PCI-Express port, and be sure it's compatible with your CPU. (The AMD FX(tm)-8350 Eight-Core Processor has an AM3+ Socket type, I think that helps.)
Case: Don't spend a ton on this. Cases range from LED-lit, with fans and all kinds of colors to what is essentially a black box. Either one works, it really just depends on your budget.
Also, ask around. I'm not the best with computers either, but building one has been pretty rewarding. Good luck.