You can certainly add a video card and improve your graphics capabilities (and performance!). You have to be careful, however. Your motherboard is getting quite old (it was built in 2009) and compatibility issues may exist with newer graphics cards. If at all possible, you should test the graphics card before purchasing.
I can tell you that I have a NVIDIA GeForce GTX 750 Ti graphics card that I use in a similar (DP55KG) board and it works very well for my needs. Whether this card is powerful enough for your gaming needs is something you will need to determine yourself...
Hope this helps,
This message was posted on behalf of Intel Corporation
N. Scott Pearson, thank you for your contribution.
To FreddyTB: as Scott mentioned, you add a video card to increase graphics capabilities.
Remember also that the system requirements may vary depending on the OS you are using, i.e: Windows® 10 is not validated by Intel for this motherboard the same happens with all the processors compatible with this board, which means that you may have compatibility issues related to the graphics drivers, therefore, adding a video card is always a good idea.
The information above is just for further clarification as the OS you are using is not specified.
Hope this information helps.