Crafting - with this bit of advice: Only do low end crafting. I have made the mistake of doing a high end crafting at e.g. 8 minutes into my 30 minute wait time and have the duty pop mid craft with 0 chance of finishing the craft HQ within the 40 seconds available. I then have to choose to gamble on reclaim, assuming it is even available, or cancel the duty, or lose the materials, or complete it NQ.

Hunts, Beast Tribes and Fates are great XP activities while waiting for the queue.
Gathering is a great revenue source.