My go-to skills are a mix of what's useful in-game and what makes sense narratively.
Interaction skills are a must every playthrough no matter what else I'm focusing on, they're just too useful and it makes sense for an empress candidate to study them.
I feel like Kxenia and Vasily's lessons are a hint that those two skill groups are useful. At first I studied Art only beause it's an interest of Zorana's friend but it comes in handy. So does Spaceship and since Zorana lives on one it makes sense she'd learn a thing or two. Engineering and Condition are also useful, and surprisingly Hunting. In early game I easily got three votes with Demolition 50, Hunting 30 and Piloting 40.
The Knowledge skils are useful in many checks plus the movement and social turn bonus, so at first I'd raise them before getting an advisor, with the reasoning that if Zorana and advisor both have 50 Bureaucracy then it's 100 in total. It wasn't until I read a post on this forum that I learned that checks don't take the sum of values but take the higher one. My jaw dropped, I was convinced they sum up. I've since reread the in-game info and in hindsight can kinda tell which part is supposed to hint at this but the phrasing was too circumspect for me and flew over my head. Now that I know I barely touch these skills since checks will be taking the advisor's value anyway unless I specialize so anything over 20 feels like a waste of class.
As for Emotions, on my first playthrough I didn't know what Empathy is used for and didn't touch it, then was flooded with multiple 'you can't tell how she feels about you', 'you can't tell if he's telling the truth', and I instantly fell in love with the game <3 This is basically my everyday life with autism so I was instantly immersed and relating to Zorana. I later found that Empathy isn't as necessary as it seems, since having it at 0 doesn't seem to affect votes and you can get opinions via poll. Allure and Menace seem to be used for Charm and Blackmail which I don't use anyway, so I tend to leave this group alone or with minimal points. Failed some checks but nothing disastrous so far.