I would highly recommend oUF_p3lim or oUF_Phanx over oUF_Simple.
If you are up to it, you could also try
oUF_Layout, which is a layout planned for learning purposes. However it is still work in progress and it lacks review, but most of the planned stuff is already in there. I'm planning a small code guide but am not sure when I'll have the time to finish it. Maybe parts of the code will change and some could get rebased to get a smoother learning curve based on feedback.
You could just follow the commits to see how the layout evolved. The prerequisites are that you know the Lua basics and get along with Github. Just ask here if you have trouble understanding something.