To expand on dungeons... Items!
It's not all about running in and hacking-slashing. There is required something rather like infrastructure, and that is the items you take with you.
On the start is potions, the most obvious thing to bring. Potions come in four flavors - health, stamina, magic, and wound. These do as expected, with wound potions being able to restore the black portion of health. You can buy simple health and stamina potions, which will do good enough in most cases, or you can craft any potion using herbs. 50 point potions and the smallest a player can craft, which is already larger than the largest potion you can buy. Two herbs make a 50 point potion, while two herbs with a base potion make a 100 point potion - base potions are bought at the healer's house. The 300 point potions require four-leaf clovers and water, which are rather rare (the clover, that is). 50 point potions are usually enough for casual dungeon runs, and producing them has a much higher success rate than 100's. Wound potions come in smaller varieties and require four herbs, including the rare golden herb, but they are very very powerful potions. It's also possible to create mixed potions, such as HP + MP potions, though generally you'll only want health + stamina to recover after a fight, or health + magic if you're using mana shield.
Potion making is helped greatly by having a homestead, where you can plant herb patches that refresh every real day.
When potions fail, you need phoenix feathers. These are simply bought, though many mobs will drop them as well. You can never have too many feathers.
Directly related to feathers are bandages. Bandages are used to heal wounds, the black potion of your HP bar. Using bandages on yourself is less effective, it doesn't restore as much. If you're sitting down, bandages work better, which makes it important to have a buddy available to patch you up. Normal bandages can be bought at the healer's house or dropped from many enemies. Handmade bandages are made using Handicraft skill from cheap cloth. They restore more wound, though there's some debate as to how much more they restore than regular. They are generally easy to make though, and they definitely do more good than store-bought. Bandages and Wound Potions do the same job. Most pets are able to use first aid, but only on their owner.
Something that a lot of people discount is firewood. Sitting at a fire greatly restores your recovery rate, as well as letting you recover wounds while in a dungeon. It also allows you to share food, which can give very important buffs. Vales Fire is an easy drink to make, which provides a massive boost to strength and a penalty to dex. Club Sandwiches are fairly easy to make, and they provide a great dex bonus. There's also int boosting food, though I can't remember them right now. A good chef will bolster dungeon efforts, but only if someone has brought firewood.
A homestead can help with firewood, but only barely. The payout rate on homestead-built chopping blocks is fairly low.
Finally, there's the actual equipment you're using. Holy Water will be nice, since you WILL die and you will want to re-bless your equipment. Bringing extra is very nice. But keep in mind that you can lose all your blessings in one KO, so it generally pays to only re-bless your weapon and/or shield, and leave your armor alone until you finish. Though this is the player's own decision, depending on how tightly they value their items and how much water they have spare. Although even with spare holy water, weapons will still break. Some very long dungeons are even enough to break a new weapon on the way down. Bringing a spare is never a bad idea. Having a gladius or even a dagger can save your hide when your sword breaks halfway through. Shortbows serve a similar duty to archers, they're small but can still be powerful when done right. While a bastard sword or a longbow might be nicer, they are larger and space isn't infinite.
And on the same note, everyone should bring a bow. Elven Short Bows are small and can be upgraded for pretty good power. Some monsters are immune or heavily resistant to melee, while some are just terrifying (ogre warriors) and being able to field a bow will make all the difference. If a smart elf is in the party, they should have brought a few quivers of arrows and be able to share ammo with any humans who want to save on inventory space. It's also possible to make handmade arrows of higher quality than store bought. These are made via blacksmithing with iron ingots and firewood, and they do more damage, better accuracy, and/or higher critical, depending on the level of arrow. This can be a major boost, especially to melee-oriented characters with low dex - the extra damage from the arrows will compensate for their lack of skill. However, they only come in packs of 100, making them somewhat awkward for elves to use, as they tend to run out. Someone using Inventory Plus premium can get a firewood bag, allowing them to carry 1x1 sized arrowheads in inventory and 1x3 sized firewood in their firewood bag, conserving inventory space and letting them craft arrows mid-dungeon.