well, you could read it as they were written, with the Talia books first, as they explain everything about Heralds. They are a bit depressing tho!
Brightly Burning is my personal fave!
Or you could read them chronologically, by starting with the black gryphon.
However, I would advise reading Talia, to understand Heralds, then maybe owlflight or Winds Trilogy to understand Hawkbrothers, then you can pretty much read any of them!