My laptop is quite old and slow. I think disabling animations would speed the system, no? Chromium is especially slow.
You can install
xubuntu-desktop and some
xfce4 packages to be able to boot into a XFCE session.
sudo apt-get install xubuntu-desktop sudo apt-get install xfce4*
Reboot and choose the xfce session at login prompt. It would be like running Xubuntu 14.04 which is a lightweight version of Ubuntu. And you can also run the usual gnome session and disable whatever you think is worth disabling.