[nambit]

Start from scratch/plain ol html. Add dependencies as you need them and for very specific purposes rather than have them "just because"

[nkassis]

Right, start with something simple, say a form and add client side validation to it. Move to making a small widget that updates with data obtained async using plain XHR. Add some styling with out preprocessors (so you know why they make life easier). Understand events and how they propagate etc. Learn a bit about the DOM and how to query it with built in apis. Etc...

Consult MDN (Mozilla developer network) and read their articles