First, make sure your portage tree is up-to-date.

   sudo emerge --sync
   sudo emerge -u world

You'll need to install the base system and some desktop environment packages.

   sudo emerge --ask x11-base/xorg-server media-libs/fontconfig \
     media-fonts/dejavu media-fonts/liberation-fonts net-misc/networkmanager \
     gnome-extra/gnome-keyring app-admin/sudo sys-power/acpid x11-themes/hicolor-icon-theme

Now, install the LXDE desktop environment along with its components.

   sudo emerge --ask gnome-extra/gnome-session \
     x11-wm/openbox x11-themes/lxde-icon-theme x11-terms/xterm x11-apps/xclock

You can use `lightdm` or `sddm` as your display manager, but for simplicity, we'll stick with the default `xdm`. If you prefer a different display manager, you can install it and configure it accordingly.

Enable and start the necessary services.

   sudo rc-update add NetworkManager default
   sudo rc-update add acpid default
   sudo /etc/init.d/NetworkManager start
   sudo /etc/init.d/acpid start

Edit the `/etc/conf.d/xdm` file to enable XDM and set it up if needed.

   echo 'XDM_LITE="true"' | sudo tee -a /etc/conf.d/xdm

Start the display manager.

   sudo startxdm