Stay in dungeons or in queue for dungeons as much as possible, as there's far more XP there than anywhere else. Start with your daily roulette. While in queue look for your hunting log targets and also pick up any FATEs you find along the way. Once you finish all your hunting log enemies, switch to picking up levequests (or regular sidequests if you have any left). If you have time for another dungeon after finishing your Roulette one, just select the top few dungeons that your level allows and queue for those. You'll also end up completing several challenge log entries in the course of these other activities, but you can check it to see if there are additional ones you can complete as well. With the 50% XP buff you get just for having a higher level class, leveling another can go pretty fast, especially through the early levels.