You need to install more packages than only gdm3, gdm3 is just the login manager.
To have a very minimal Gnome desktop environment, you need to install the following packages (maybe some are already installed in your system):
sudo apt-get install -y ca-certificates libgl1-mesa-dri x11-xserver-utils fonts-cantarell gdm3 gnome-session gnome-shell gnome-themes-standard gvfs-backends gvfs-fuse mousetweaks network-manager-gnome pulseaudio sound-theme-freedesktop xdg-user-dirs
Hope it helps :-)