PotD is unlocked in Gridania Adventures guild.
Its good exp below Lv50, and ok exp above Lv50.
at Lv61 Heaven on High is the replacement, and is much faster exp. (and with how long it takes to get a group, even as tank or healer, due to everyone going to heaven on high, this is still better. no point in waiting 30+min as a tank or healer)
heaven on high is in the ruby sea. i forget where the quest giver is, but you'll find them.

anyways, stop the MSQ, and just get a job to 70, so the GNB will gain more exp faster, and u wont have to frequently stop and grind, mid story.
(also do the roulettes once a day to get a chunk of exp needed, which helps a ton in the 60s. not so much trials, 50/60/70 dungeons, and leveling roulette only gives decent exp if its within 5-10 levels of your current level, or sastahsa/tam tara/copperbell. if u get something like haukke manor, you're honestly wasting the roulette as it wont even give you a 10th of a levels worth of exp. (sastasha, w/o a roulette bonus would give u more exp from the mobs alone) so yeah, its a bit of a gamble, due to how they messed with it in secret over time.))