This setup eliminates most of the services that will slow down your system (like the synaptic cache generation utility, etc.) and also remove nautilus (which consumes a shit load of resources) and replace it with nemo and replace _gedit _with geany. This means you will lose the ubuntu-desktop package.. but it wont hurt you.
Most importantly, this will replace Unity with Gnome** Shell **(for performance), but I just love the flexibility of extensions.gnome.org to miss it.
This setup should take less than 400 mb RAM on startup.