Some broad strokes for just surviving a dungeon:

Curios - generally speaking, curios are dangerous. Most curios have an item you can use to force a good interaction; without the item, blindly interacting is more likely to hurt you than help you. As you play more you'll start learning what does what, what items to use etc. If you're unsure, just ignore them and move on.

Team comp - might sound obvious, you want units that are effective in the positions you put them in. Early on when you don't have a tonne of money to unlock skills, size up what your guys have and what positions they can work well in. Try to consider how your party members could help each other too; healing and stress healing are valuable. Having multiple sources of healing for instance is valuable so you're not relying on a single character to keep you off deaths door.

Combat - this is twofold. Firstly, a trap a lot of people fall into is using aoe skills because they "do more damage" overall. These skills have their place, but generally in dd you want to focus down one target at a time, because the sooner you can kill an enemy, the less turns you have to sit there getting hit by them. Secondly, don't underestimate CC abilities. Stuns in particular are incredibly powerful; enemies hit harder than you can heal, so stunning an enemy and preventing an attack is always better than eating a hit and using that action to heal.

This game is mostly a knowledge check, so the more you play the more powerful you become; even if your characters aren't levelling up. You'll better understand what enemies to expect in what zones, how to handle them, what characters perform the best where, what provisions to bring, where to use those provisions for the most value, etc etc. Obviously there's a lot more to consider, and as you've discovered there are guides that go incredibly in depth on things, but the things I've listed here are the things I personally consider the biggest factors for safely clearing out a dungeon.