End goals......that's easy.
I usualy use 2 options to start my end game(actually it's the most lenghty one).
1) The sneaky way.Remain a mercenary until you can field 200 soldiers, then take a castle, get all the lords you are friends with WHILE a faction is at war with someone else, at the begining of their war. Declare Pendor then. As a mercenary you get a lot more denars per week, as a vassal you get about 800 denars from a fief aka village wich is raided most of the times by the npc.
2) The funny way. Find the "rightfull heir" to a faction, each faction has a hero character wich wants to remove the curent leader of that faction. He joins your party and is a strong hero, you begin to conquer teritory for the "new" faction and some lords may join you, he is 100 relation with you.
Also, make your heroes the best warriors in your army, with ranged/melee and cavalry items. Yes, all of them to change them when the situation requires it. Like when you get 40 cavalry and hunt down all enemy lords or ranged for siege. Have lots of troops in your castle/city, more than you need, to be well defended and be prepared for everything.
Pop doesn't have 3 types of units(ranged, melee and cavalry). It has a looot more like heavy infantry, anti cav infrantry, super heavy infantry, heavy ranged infantry, throwing weapons infantry, siege infantry etc.
So for all these you need the training skill, give a few points to all heroes in training because you can't train troops OVER your level, if you give all some training(especially high level knights, you can have only 1 or 2 knights( example: Sir Alistair) they will train them and help a lot. At the end game i would train all troops daily.