Okay, here are a couple of guys worth watching. Incomplete but hopefully helpful:
The leads:
Yang Wenli
Reinhard von Lohengramm
Basically our two principals this season, we get quite a bit of character development and personality and so on.
Imperials to watch:
Siegfried Kircheis
Reinhard von Lohengramm's dearest and oldest friend, very important character.
Mittermeyer
Reuental
You might remember these two guys as the guys who aren't in the battle but are commenting about how they hope Reinhard wins. What the hell is with that, eh? Well, they're two of his most loyal and trusted lieutenants based on previous campaigns so they'll be a big deal. They were swapped out of this campaign by Reinhard's enemies, who figured that without his best officiers Reinhard can't win battles.
Oberstein
Don't think he's appeared yet but wait for this guy. I love this bastard, and he loves his dog.
Prince von Braunschweig:
Pretty much the epitome of the arrogance and presumption of the Goldenbaum Dynasty's aristocracy. A total and utter prick to put it nicely, and a rather darned important one.
Alliance guys to watch:
Juan Minci:
Yang Wenli's ward. That's pretty much all he is now but he's the guy Yang Wenli has the closest connection to.
Greenhill:
I forget his first name but the father of Frederica Greenhill and a man Yang Wenli rather respects, one of the more trustworthy Alliance characters.
Job Truniht:
The good and decent El Presidente of the free democratic order. Ha, I kid.
Jessica Edwards:
You'll like her. A lot.
Others:
The leader of Phezzan who's name I can't remember I'd look it up but I have to go. The bald guy.