Dungeon Progression Guide
This is a rough outline of what dungeons to try as your power grows, however take note difficulty of dungeons can greatly vary depending on your main skill set as well as party size.
It is recommended to try a variety of dungeons as you become stronger to familiarize yourself with everything available.
Ciar Beginner
If you are just starting out and don't know what to do, Ciar Beginner can be a great way to get familiar with some basics and get your first few APs, you can get the Ciar Beginner Pass from Ranald at any time.
Ciar Normal / Math Normal
These are dungeons similar in difficulty, and can provide cheap leather pouches (and common leather pouch from Math) which can be coveted items by many players.
These dungeons are also a good source of leathers, which you will need if you plan to rank weaving and tailoring.
Rabbie Normal / Rabbie Basic / Albey Red
Normal is a slight step up from Ciar, and a good introduction before going to Rabbie Basic, a dungeon which can be good for gold as skeletons here often drop fomor scrolls which can be exchanged for gold. Albey Red is similar to Rabbie Basic, but much shorter.
Metal Skeletons can also drop the Fox Enchant, and Skeleton Wolves drop Fox Hunter's Enchant, which can be a decent source of extra damage early game.
Karu Normal
Karu has fairly weak enemies, and from it you can also gather exploration XP (check for exploration quests as well!).
The dungeon also drops various skill books which can be useful as well as traded to other players.
Quartz Enchant can also drop from here, another useful beginner enchant.
Fiodh Normal
Werewolves are a decent source of XP if you are still on the weak side, and all Fiodh Dungeon variants have guaranteed homestead seed drops, which is great to progress your homestead.
Hardmode Alby Normal and Ciar Normal
Starting at total level 250 you'll be able to access hard mode dungeons, Alby and Ciar normal versions are good experience as they offer fairly weak enemies in decent density. Alby Normal HM can drop Cobweb Pouches.
Alby Intermediate
A good introductory dungeon to handling multi-aggro enemies, as the ones that multi-aggro have low HP compared to others.
Forgotten Waterway
Can drop several good enchants, handling of multi-aggro required unless you go in with at least a small party.
Coil Basic
The best source of White Herbs, as well as good pre-enchanted headgear.
Mysterious Imp Forest
Source of the highly coveted Exploration Mastery: How to find things book, as well as Ambush Enchant.
Great source of XP, and exploration XP, look for Exploration Quests to kill the boss imps, as well as forest captain.