Upgrading your toons might, skills, enchantments, crafting and hero tokens are some of the things we are all constantly dedicating time to. While I don't recommend it as a first choice, one way of doing it efficiently is to farm gem shards from Dungeons.
When first playing the game, the fastest way to advance, is to constantly quest until all quests are complete. When it comes to shard farming I recommend skipping the collection of Tier 3 gem shards entirely. How you allot your time and "energy" is essential and it is much more rewarding when focused on the tasks that get you the most. Completing all quest lines will get you all the way to level 32 and allow you to then change your focus to high level raids and their rewards including the ability to farm the necessary ingredient items needed for enchanting and crafting while getting the highest payoff for the amount of energy spent. If you can advance by skipping to higher collectables and raids then you can avoid spending valuable time working on things for your toon.
If you are capable of entering the Vile Realm Gate area, by unlocking The Undrian Plateau in the SE of your World Map, then you might consider raiding those dungeons since they drop Tier 5 shards. In addition, the Vile Realm Gate area drops essence, refined essence and flux anywhere you go.
~ Gem Shard Locations ~
Tier 3 Dungeons:
Hunter's Folly - World Map - Red (Level 18-20)
Edda's Keep - Dragonmoor - Blue (Level 16-19)
Ice Dragon's Lair - The Frozen Vale - Yellow (Level 20)
Tier 4 Dungeons:
Hall of the Goblin King - The Undrian Plateau - Red (Level 26-28)
The Vile Gate (LoB: Lord of Blades) - Undrian Plateau - Yellow (Level 27-30)
The Emperor's Court - Fellmarsh - Blue (Level 24-25)
Karnak's Temple - Shattered Plane - 2x T4 Random (Level 27-30)
Tier 5 Dungeons: (Vile Realm Gate)
Callisto's Keep - Mistwalker Woodlands - Red (Level 30-31)
Disturbed Grave - Accursed Steppe - Yellow (Level 31-32)
The Prince of Blades - Accursed Steppe - Blue (Level 31-32)