Now for battles. My army composition consists of mostly foot units. The ratio of inf/ar/cav I maintain is around 4:3:1. Rhodoks are easily the best infantry because of their pikemen, and you're going to be needing more than a few in your army, trust me. Infantry soak up the enemy charge, archers cause the most casualties and cavalry kept back to assist at crucial moments or mop up archers. Before the battle use the planner. Infantry should be in ranks or shield wall, stand closer, weapon orders - polearms. I keep cavalry in wedge just so they don't spread all over the place - I find it easier to control them that way, but it's up to you. Learn hotkeys you'll need them. The chief hotkey you'll need is "hold fire/fire at will", "stand ground", "stand closer", "charge" and "assume formation". Don't forget to organize your units in control groups - I use 123 for inf/arch/cav and 4 for Heroes whom I keep back so they survive till the end of the battle (if your "surgery" guy dies early on...then say good bye to a good chunk of your force). In case you didn't know it, pressing and holding F1 also orders the selected group to move where you point it to or attack an enemy group.
So at this point you should be easily running/upgrading a warband of ~130 troops, your money troubles are no longer an issue, and where to go from there is up to you. You can either swear allegiance to a faction, or better yet capture a weakly held castle and town to start your own.