Must-have: Interaction (especially Etiquette) and Emotion (especially Empathy—knowing who likes and dislikes me feels vital). Any time I skimp on these I suffer for it.
Useful: Piloting comes up more than I'd expected! Also Engineering and Arts, and Endurance specifically in the Body Control category.
I'm not yet at the point of writing anything off. I haven't yet focused on Stealth, but I've failed enough Stealth tests to see that it can be useful. Domination seems limited, but there are several quests where it also seems necessary. I haven't explored Combat, Condition, or Environment yet.
For the most part I neglect knowledge skills for Zorana and focus on hiring skilled advisors (with a couple of exceptions—I'll learn a bit of Spirituality just to make good impressions, I'm currently experimenting with Galactic Relations, and the super-Intrigue run I did was interesting even though it was a little immersion breaking that everyone had identical military/intrigue/spirituality stats). Science and Bureaucracy are the most vital in my experience—the movement speed and extra social action are both super useful.