Patience. Taking this farming journey slow is the way to go. There is a huge list of collectibles costing Resonance Crystals, ranging from transmogs, battle pets, toys, The War Within mount schematics to housing decors.
In this page, I will share the farming methods I use to rack up this currency efficiently and make the AllTheThings addon creators proud.
Pro tip: You can start each week with forging a pact with The Vizier for the buff World Buff: Vizier’s Supremacy which increases all Kej acquisition by 20%, useful for the last tip in this page!
Without further ado, the list of methods I use are as follows:
Awakening The Machine

This is the weekly activity in Gundargaz in The Ringing Deeps. This might be the lowest effort Resonance Crystal farm on this page, netting at least 300 Resonance Crystals per week per toon (yes, you can do it on multiple toons in the same week, but note that the reputation reward is given to only the first toon of the week).
100 (5 from each round) will come from just completing the waves and about 200+ will come from the chests.

I park a few alts in front of the NPC, and each week I will log in to do this quick, weekly event before logging onto other alts to farm other stuff!
Call of the World Soul
This is a good source of Resonance Crystals that can be completed alongside some other activities that grants Resonance Crystals. However, this quest is not always available every week.

This quest is provided by Faerin Lothar in Dornogal, right outside the inn. One of the best option would be the Worldsoul: Awakening Machine quest where it can be done concurrently with the activity above. Another good option will be Worldsoul: Forging a Pact where its objectives will coincide with the stuff you do down in Azj-Kahet.
Archives: xxx Quests
Similar to Call of the World Soul, this is a good source of crystals that may not be available every week. This quest is provided by High Speaker Brinthe, right across the table from Faerin Lothar.

This quest requires you to obtain 100 Titan Disc Fragments, which can be obtained through many ways, delves (giving about 30+ each run), dungeons, treasures across Khaz Algar, rare mobs, etc.
A good way to obtain a good amount of the quest item is to run follower dungeons, which as luck would have it, coincide with another quest that rewards Resonance Crystals (see Weekly Dungeon Quest below).

Though it should be noted that you would have to supplement a single run of follower dungeon with more follower dungeons or other sources as each boss only gives 15 Titan Disc Fragments.
To turn in this quest, you have to enter the Waygate(/way 30.61 59.64, TomTom coordinates) where Dagran Thaurissan II awaits.


Weekly Dungeon Quest
This quest is provided by Biergoth, close to both Faerin Lothar and High Speaker Brinthe. She offers a quest every week, requiring you to complete a TWW dungeon.
Your first completion of this quest on any given week will grant you a 1500 reputation reward to any TWW faction. Subsequent completions in the same week (on other characters) will reward you with a choice of either 115 Kej or 225 Resonance Crystals.

Delves: Worldwide Research
This is a weekly quest provided by Brann Bronzebeard in Dornogal, requiring you to complete 3 delves. You can quickly complete this quest by completing 3 Tier 1 delves.

Similar to the Archives quest, the reward is a chest that grants 900 Resonant Crystals and 450 Kej.
Key to Success
Talking about delves, your first completion of a delve (any tier) for the week allows you to loot the quest item Archaic Cipher Key from the rewards room at the end of the delve. Turn it in to Elise Starseeker, who is in the same area as Brann in Dornogal.

The quest rewards you with 300 Resonance Crystals, a nice weekly bonus for something you already would have done for Delves: Worldwide Research!
Flaming the Light

This takes place in Light’s Blooming area in Hallowfall.
The Resonance Crystals in this section comes from 2 sources:
- Quests from Lesser Keyflame NPCs, and
- Bonus objectives from Light Blooming’s Keyflames.
To spawn the quest NPCs, you will need 3 Radiant Remnants to fully light up a Lesser Keyflame.


Most of the quests from these NPCs will grant a Lamplighter Supply Satchel each which has a chance to drop the Dauntless Imperial Lynx mount and a small amount of Resonance Crystals.
However, the bulk of the Resonance Crystals will come from the Bonus Objectives.

These Bonus Objectives are available to you when a large Keyflame is fully activated. This is done by using 20 Radiant Remnants. The good thing is that other players can also contribute to the 20 needed. Once lit, you will have 20 minutes to complete the Bonus Objective before having to refill it with more Radiant Remnants.
The reward for completing any Bonus Objective is 200 Resonance Crystals and a Lamplighter Supply Satchel.
Ecological Succession
This weekly quest is available in K’aresh, specifically The Oasis. For this weekly quest to be available, you have complete the entire quest storyline for The Oasis.
To gain progress in this quest, you can either do the individual weekly quests given by the NPCs in The Oasis, defeating Sthaarbs, turning in the quest Making a Deposit (starts from picking up the anima item from the boss mob at the end of Devourer Invasions), and/or complete mini-tasks in the area, such as:
- Watering the plants,
- Leveling the Torn-up Earth,
- Collecting research from Data Collection Drones,
- Interacting with Visiting Brokers,
- Fishing Hydrobites

Ecological Succession rewards a Wriggling Pinnacle Cache which contains 900 Resonance Crystals and 450 Kej. A bonus is that the first Cache you open each week gives a guaranteed pet or mount!
Don’t Forget! Kej to Resonance Crystals Conversion
In The Weaver’s Lair, Ajz-Kahet, you can convert your excess Kej for Resonance Crystals with the NPC Ka’muko (/way 56.6 42.94, TomTom coordinates), at a rate of 2000 Kej for 1000 Resonance Crystals.

Throughout your journey, the Kej you receive will be amplified by The Vizier’s buff. Soon enough, you’ll have lots of Kej to convert to Resonance Crystals!
Conclusion
And these are the major sources of Resonance Crystals that I have been farming and would love to share them with the world! 🙂 The best way forward would be to coincide quest objective so that you’ll gain progress for multiple quests while completing a single task!
Good luck fellow collectors and I wish your Resonance Crystals (and other collectible) farming journey to be a quick and smooth one!