Did my first goblin den dungeon and the reward was ok... though a little underwhelmed at the lack of power behind overgrowth. I'm guessing I need better magic stat
I forgot to mention this in my little guide, but make sure to pick the mage guild when you're choosing which guild to focus on. That will give you a free staff along with your first slave. Also the first couple of days do a date with your first slave and once you have her mood maxed out pick the wits training option. That will give a nice boost to wits for both the MC and the slave which will increase both of their damage (Wits determines damage, not Magic).
You will randomly get staves as loot from dungeons (that's why you need someone with the thief class to open locks) but if you get unlucky and don't get one from the first few dungeons, definitely buy one from the shop if you see one there. Any weapon is better than no weapon but the staves make a huge difference for magic.
Usually by day 3 my first 2 characters can 1 shot everything in the bandit fort with overgrowth except the ballistas, the golems, and the assassins. Blizzard is similarly useful except that it got nerfed in the latest update and costs mana now so you'll burn through all your mana potions if you have to rely on that. It doesn't do quite as much damage as overgrowth but it has a really useful slow effect as well.
One of the other big benefits of clearing out dungeons aside from the resources is that it's the fastest way for both your MC and slaves to gain skills and class abilities. You will mostly gain wits and physical this way but you can use the xp to buy things like harlot, geisha, etc that will dramatically boost social and sex skills as well. XP from sex is a lot slower. Bumping the physical stats for a bunch of slaves will increase the speed that they gather resources and upgrade your base. Increasing wits will speed up gathering food and some crafting stuff. You also will get xp scrolls as rewards from the final chest which you can use to level up anyone you want.