Mixing it up helps a ton, if your in no rush to 60 then take your time and enjoy the game, the best time to enter a dungeon is when you hit the min Level requirement for it as defeated mobs will yield chain exp bonus then. Seriously the amount of Exp you get is awesome but once you get past that Min level require you wont get as much.

But yeah mixing it up a little, leve quest, fates, beast tribes, roulette's leveling and LV50.