So a couple of tips I’ve learnt along the way: what makes a killbox work at all is managing how you can be attacked in the first place. If you can decide the battlefield and delay them as long as possible to be fully prepared, then you’re going to be a lot better off. Use traps everywhere, have more turrets than you do people, use artillery when you can, and give your enemy no cover to work with. It doesn’t have to be a killbox, but plenty of damage along the way and natural choke points can often defeat a raid before they can even score a hit.
The main point of wealth is that it scales the size of an attack proportionally. People have the greatest weight for wealth, so make sure you can hold off a raid before recruiting 20 prisoners. I don’t usually worry too much about keeping wealth low, but you see harder raids if your wealth has outpaced your defence.
The wiki also has plenty of solid strategies for defence if you’re stumped, and often working with the environment you’ve got can be much more fun than creating an artificial killbox (in my opinion anyway). Good defence is the basis for completing any of the quests I’ve found, so surviving long enough should absolutely help complete them.
Edit: I’d 100% recommend the game to anyone who’s interested in a colony builder that’s got a decent focus on survival, I’ve seen many hilarious and really fun things happen with a story that comes simply from chance.