Originally the series was meant to be written around 5 main novels, with everything else in between being filler like Shadows of the Empire. It goes: Vector Prime, Balance Point, Star by Star, Destiny's Way, The Unifying Force
Not sure if this holds up as a reading order though. Some of the better character driven stuff ended up in other novels. If there's a single book out of the entire series worth reading it's "Traitor".
Even so, it can be hard to get into the series nowadays because it was very much a product of its time (Empire fatigue, invincible protagonists, most stories before it being self contained).