For quest rewards I always took the cash because I was leveling crafting at the same time and making my own stuff
By the way, the quests don't reset when you are leveling a different class so you can only complete each quest once - so don't rely on the quest rewards for your equipment.
The only reason to level one class first is that all lower level classes receive a 50% xp boost. So it is better to have one "highest" class but it doesn't need to be much higher than the others.
Other than quests, do your hunting log and guildhests.