Mix in a little bit of everything. Your challenge log (unlocked at the Drowning Wench in Limsa) combined with daily roulettes, some leves, a bit of FATEs, and so forth will give you the most amount of experience for your time. Dungeon experience has been boosted a significant amount and your best bet after your daily experience bonuses have been used is to keep queueing for the highest level dungeon that you can while grabbing every bit of experience in the open world while you wait on your queue.