One of the core tasks that one needs to perform per character at max level is increasing their resistances permanently. Do not craft temporary resistance potions using the elements material that are dropped in dungeons (dungeons that have special element properties have a chance to drop that respective crafting material). Save those for actually crafting the elemental essence (a consumable potion) for each level.
There are 3 levels per resistance (bring up your character profile and click the resistances tab at the top right corner). Level 1 has two essence slots (Level 2 has 3, and Level 3 has 4). Crafting the essences requires Wild Azalea and for Level 3 ones, each craft consumes 45 of them. Basically, you need a total of 720 Wild Azalea to craft all levels of essences for all the elemental resists.
And these do not drop in large quantities. Players who never played during the betas initially leveling wonder what a lot of these material drops are for. Well, they are all used as supplemental material for end game. Wild Azalea’s drop in normal mode dungeons but not all of them drop significant quantities of them. The Ruined Citadel is one of the more fruitful ones (I’ve gotten like 12 of them during +3 runs). Most of the material drops while clearing out the dungeon so do not use an Invasion Ticket for this dungeon. So yeah, you need to grind out a large number of normal dungeon runs (they are sold in the auction house but cost a ton of gold). Nanus pet (auto loot pickup) is recommended since it will stop you from going crazy picking that stuff up yourself.
Pro-tip: if you want to make tons of gold, create a speed spec and farm Wild Azalea’s.
Doing Dimensional Rifts also drop Wild Azalea (2-4) if you bored of running Citadel so this is where area coins come into play. Those can be spent at the token vendor in that same zone for its Dimensional Rift key (that is except the initial Cracked Temple one where it is part of the quest where the key is under a rock). You can farm that rock and key (so long as the quest hasn’t been completed earlier) and just do that rift over and over. Likewise, you can also assist lower level players since Dimensional Rifts are open co-op events that anyone can join. The goal is to spam clear these rifts so its best to just do ones that you can quickly one shot everything. Kafka Canyon is the next earliest zone. If you lack area coins, those can be acquired either doing that zones Infinite Hunting Grounds or salvaging rares that drop in this zone.
