I'd personally suggest adding about 2GB of RAM. But for comparison, here's my specs. I got them all on pcpartpicker.com so you can go there, find what I used, and compare prices. If you're not comfortable upgrading the parts yourself, do a Google search to see which computer stores in your local area will upgrade it for you and how much they charge. Some Best Buy's will send the Geek Squad out to your home to do it for you. (Even I still feel uncomfortable messing with the interior of my PC)
GPU (graphics/video card) NVIDIA GeForce GTX 770 (bought through Asus)
CPU (processor) AMD FX 4130 4 (quad) core. I run every game perfectly with it, maxed out about 55 fps. But I'm upgrading to AMD FX 8350 for future gaming.
RAM (memory) Kingston Blu series 8GB (2x4)
Hard Drive: Western Digital 1TB
Motherboard: Asus M5A97 LE R.20
Power Supply: Corsaire 600 watt
Operating System: Windows 8.1 64 bit.
Case (just for the Hell of it) Coolermaster HAF 912