Disregard errands, build armies.
The quests are lame, make your own story. That's where the fun is.
Pick fights, raid caravans, beat up bandits, turn your little band of farmers into a badass group of mercs and beat up anyone who says otherwise (avoiding lords, of course, at least until you're nice and powerful).
Then seize your own castle and build your MIGHTY BANDIT KINGDOM from there.
One of my favorite "storylines" to play. M&B is all about telling your own story. Like Minecraft. It's best when you give yourself a project and work at it.