I use a tiling window manager i3-wm with xorg-xserver and tmux/screen when xserver is not running. I use lightweight applications. Also I disable all unnecessary processes to make it the most lightweight.

My thought goes to The Human Ape project- a pioneering project to study and rescue a disappearing tribe. Read details at http://www.betterplace.org/en/projects/4597-human-development-intitute and http://thehumanape.org/ if it helps.