For players looking to acquire more Resonance Crystals to purchase Renown Rewards in the War Within, gold completions of Skyriding Races in Khaz Algar award a significant amount per character and can be transferred via Warband.
Khaz Algar Skyriding Races
Council of Dornogal Renown Assembly of the Deeps Renown
Hallowfall Arathi Renown Severed Threads Renown
Renown offers an excellent way to help outfit your characters with some powerful gear (ilvl 384-397 + upgrades) early on in the War Within, but the gear can be expensive in terms of Resonance Crystals.
Early gear, such as Noncandescent Smithing Hood, costs 2600 Resonance Crystals with later pieces costing as much as 3900 and you'll need to pay that for each character you're outfitting. Factor in all the mounts, appearances, toys, and pets available from Renown and Resonance Crystals will definitely be valuable for some time.
Council of Dornogal Renown Vendor
You'll have plenty of time to collect Resonance Crystals while increasing your Renown, but if you're looking for a quick infusion then you may want to consider Skyriding races.
Skyriding races (previously Dragonriding races) have returned in the War Within and they're a quick way to earn some Resonance Crystals per character that's completely transferrable 1-to-1 across your warband.
The first time each character completes a skyriding race in gold time, you'll earn 95 Resonance Crystals. With 3 courses per skyriding race (Normal, Reverse, and Advanced), 6 races per zone, and 4 zones, you can earn 6840 Resonance Crystals per character.
That amount won't be enough to purchase all the gear pieces across the 4 factions for each character, but it should give you a headstart. You could instead funnel those resources to your main if you so choose.
Below are the locations of the all the Khaz Algar Skyriding races for easy reference. Fair winds and fast travel, racers!