If you are gaming in 1080p-resolution, then the GPU is sufficient. Upgrade your CPU, MB, and RAM. Install an SSD.
If you are gaming in 1440p-resolution, then, upgrade your GPU, CPU, MB, and RAM. Install an SSD.
If you are still gaming in 720p, then, upgrade your monitor to a 1080p/144Hz with G-Sync. Upgrade CPU, MB, RAM and SSD.