software recommendation - lightweight window manager/desktop environment similar to Unity

I am looking for a lightweight window manager/desktop environment similar to Unity,
but not Unity/Unity-2D GNOME or KDE. Specifically, I'm looking for something light with the following features:

• window buttons layout like in Unity.




• side bar/dock on left with system tray, apps, devices & a menu of some sort.




• or a top bar with system tray, apps, devices & a menu of some sort.

The reason I am looking for this is that my computer can't handle Unity & my development apps at once any more.

You may also want to have a look at Xubuntu that comes with the lightweight Xfce desktop. This also includes a customizable launcher (here shown at the bottom) that can also be moved to the left side like in Unity: