to CAD? Or not to CAD?

So I’ll be starting my BA Hons in Architecture at University of Westminster in about a month or so, and I wanted to start teaching myself some CAD (I always wanted to learn!). So I was wondering what you guys recommend me learning. I’m thinking I have three main options:

Revit AutoCAD

Graphisoft ArchiCAD

or

Sketch-Up

Which one do you think I should invest some time into? Keep in mind i’m on a Mac.

Thanks!