Ubuntu Server by default does not intentionally designed to have a graphical display, only text mode, because ubuntu server is one of the many OS Server that is safe and stable, to maintain the stability of ubuntu server, typically an OS just installed the necessary applications only, not to install any application, could have given the Ubuntu Server GUI the same as Ubuntu Desktop.
sudo apt-get update
Wait until finished.
Then Upgrade (recommended).
sudo apt-get upgrade
It depends on the system you install from scratch, can not be long.
Only then Install GUI.
One can be chosen depending on individual taste.
sudo apt-get install ubuntu-desktop
sudo apt-get install kubuntu-desktop
sudo apt-get install xubuntu-desktop
sudo apt-get install xorg
sudo apt-get install xorg lxdm lxde
sudo apt-get install xorg lxde-core lxdm
sudo apt-get install xorg xfce4-core gdm
sudo apt-get install xorg gnome-core gdm