I haven't installed any graphical interface like X Window on Centos, and found its solution how to install it for my personal purpose. Please take a look below steps to install "Gnome Shell" as a main graphical interface.
STEP 1. Install X Window System
STEP 2. To add the Gnome Shell desktop on CentOS 7, you would do:
This would provide you with a minimal Gnome Desktop environment. You do have to do a couple of other steps:
This will allow it to start on boot as you are setting it for the default boot target runlevel.