Learn the lone sword first. Its principals and techniques will serve you well when you pick up the dagger; and for that matter any other weapon. If you are confident with it, you will learn any other combination that much easier.
All the principals of the sword are founded in the four guards, including all of the other postures and counter-postures, tempi and contratempi (time and counter-time), cavazioni, contracavazioni, ricavazioni, half-cavazioni, committing the sword, etc. In short you can’t do anything without being in the framework of the four guards. (Lots of variations to follow.)
I’m going to teach you which techniques to use when, but really if you know what you are doing you will just know how to react to any situation. (Sounds a lot like Meyer, no?) That said, some postures are better than others and what’s good in one measure may not work in the other. (There are two measures in Fabris’ system.)
But first lets concentrate on the four guards: 1st, 2nd, 3rd, and 4th.