Since you are gaming I'd suggest a gpu upgrade due to the fact that processor is still capable of gaming at high settings if you have the gpu power to do so.
Aswell as this if you were to upgrade the cpu to something recent you would have to buy a cpu motherboard and ram (ddr4 ram is very expensive)
I'd suggest a 1050ti if you are gaming in 1080p as it has the capabilities to run most games at high.
If you are going to be playing in higher resolutions id suggest waiting until the new gtx 11 series is released.
Hope this helps
Tyler