To install it via CLI, perform the following commands:
apt-get install aptitude tasksel tasksel install gnome-desktop --new-install
apt-get install kde-standard
apt-get install xfce4 xfce4-goodies thunar-archive-plugin
apt-get install lxde
Here Gnome, KDE, XFCE, LXDE all provide GUI environment for debian. A single GUI environment is enough to run on the VPS but please go through " https://wiki.debian.org/DesktopEnvironment " to find out the best suitable GUI for your needs.
To connect to the GUI via VNC/RDP, please see -- How to install a xRDP on Debian 9