Graphics Card

My first build, I finish everything and come to find out that I need a graphics card just to boot. I was already planning on this, but just hoping to be able to save up a bit and get a good one, but it looks like I'm getting an early upgrade.
Anyways, I need some help on which one I should get. Nvidia or Radeon, how much memory should it have? I'm new to all of this so bare with me. I'd like to spend the least amount possible, but if I have to pay around 120$ I'll live.

CPU - AMD Athlon II X4 750K 3.4GHz Quad-Core
Motherboard - Gigabyte GA-F2A85X-D3H ATX FM2
Memory - G.Skill Ripjaws Series 4GB (2 x 2GB) DDR3-1333
Storage - Seagate Barracuda 1TB 3.5" 7200RPM
Power Supply - SeaSonic 380W ATX12V

Those are my specs, I want to be able to play games like Starcraft II smoothly, or Civ 5. I'll be doing my FPS gaming on a PlayStation, so I don't need to able to play things like Battlefield at max settings, however I'd still like the games I play to run smoothly. I'd also like to not have to buy a new one for at least a few years, so something reliable or with a warranty is important, not going to want to have to spend a couple hundred dollars on my computer during college.
Thanks!