After finishing Mansa and Hiawatha I have generally put most of my workers in the University. I currently have 11 researching. But If I were to try and suggest how to prioritize I would want to know which Barrack attack troops you use the most when you play. Then work on the branch in the University that improves those, so if you mostly use Artillery the long road along da Vinci may be best, if you mostly use infantry the short road for Catherine would be my suggestion.
I would prioritize researching under leaders that prioritize offensive upgrades such as Leonardo Da Vinci and King Sejong.
What they said...... But If I were to try and suggest how to prioritize I would want to know which Barrack attack troops you use the most when you play. Then work on the branch in the University that improves those,
Sejong is my choice mainly. First tier only 'costs' 2 citizens and I got all of them to at least lvl 5 so that I can continue with 2nd tier. My first bigger aim here is protect tactic, which is his 3rd tier research with (I guess) 4 citizens. A 30% to protect tactic time would be a great boost and I estimate that it would last for 1min if fully upgraded. I could then use my second protect tactic for something else, maybe.
Of course, the ultimate goal would be to fully upgrade Sejong for the 1 citizen research reduction. Being at 22/100 though, I estimate, it would take years to finish.