Want a good gaming GPU for high end graphics, but.....

I don't want to spend over $100. I know there are not many cards out there that can do this for that price, but hopefully someone out there can help me.
These are the game I plan on playing on my computer.
- Guild Wars 2
- Minecraft
- Grand Theft Auto IV and V
- Just Cause 2
- Skyrim
- And a lot of not so demanding graphics games like Bastion, PvsZ, and some arcade games.

This is my setup so far......
-Western Digital Cavier Black 1TB SATA III 7200 RPM 64 MB Internal Hard Drive
-Asus 24x DVD-RW Internal Optical Drive
-WIndows 7 Home Premium
-Cooler Master eXtreme Power Plus Series 500W Power Supply
-GIGABYTE GA-970A-UD3 AM3+ AMD 970 SATA 6Gb/s USB 3.0 ATX AMD Motherboard
-Kingston Technology HyperX Blu 4GB 1333MHz DDR3 Non-ECC CL9 DIMM KHX1333C9D3B1/4G
-AMD Phenom II X4 965 AM3 3.4Ghz 512KB 45NM 125W 4000MHZ

I have only bought the motherboard, processor, and ram so if you have any suggestions or comments on the items I have chosen please feel free to express them.
Thanks ahead of time.