Your CPU is very weak. I wouldn't suggest even a 1060 with your CPU. You may could tweak the system and game and maybe get it to 50fps. Use blackvipers safe desktop settings to free up CPU resources. Use cclearn to clean up your registry.
http://www.blackviper.com/
http://download.cnet.com/windows/
Here is a CPU optimization guide for CPU's.
http://www.gamersnexus.net/game-bench/1909-gta-v-graphics-optimization-guide