Good crews are important for farming:
- Assistance with particularly difficult and/or numerous enemies
- Buffs, especially Divinity and Coyote Spirit which include a luck bonus at higher rage ranks
- Ghi meter bestows passive buffs; a full crew keeps the Ghi meter full.
As for farming locations:
- Readily-accessible boss instances. Kat's Doll and Papa Saw are ideal since they spawn lots of minions, but if you're too low-level for that, General Mayhem will do in a pinch.
- Repeatable "kill X enemies of this kind" quests in every area once you're done with the storyline quests.
- The Hive is pretty underrated, but a good Hive crew can easily farm bugs for hours.
- Areas with lots of chests: Endgame areas are really awesome for the sheer number of chests they contain, as well as numerous high-loot enemies.