Gosh it's been ages since I last fired this up.
Best to start with Teiris or Wein. They are the basic ones and picking either of them it is best to seek each other out quickly so you can team up.
You get a few generals that like to run off and betray you but I think you find loyalty coins and give them to those usurpers.
Domestics is kinda boring but is where you do the important stuff like fortify your castles, and convince generals to join your quest.
Mages and Archers are the tricky ones. If you are controlling these hordes Mages and archers are best left standing until you are comfortable to send an all out melee attack or to forward them over to the enemy and have them surround the general.
If you are facing Mages and archers keep a few men stationary surrounding you and send your main formations to the edges of the screen where they run up and spread around the edges of the map till they get to the enemy general and have your men surround them and they can just be stationed and just fire projectiles.
Harpies, Dragons, Zombies, Monks, Samurai are the most trickiest to deal with but generally if the opposition sends their army towards you, you just have your own army stationed where you have about 10+ of your own men surround you. and the rest will just stand there and cut/shoot down the opposition.