Seriously, how...

[Nomad-phx]

Hit lvl 56, start spamming blue scrip turn ins. Infinite allowances+the exp you get from crafting the turn ins.

[Lemuria]

Hit lvl 56, start spamming blue scrip turn ins. Infinite allowances+the exp you get from crafting the turn ins.

Sadly, this is almost the single most inefficient means of leveling up as well. The average collectible hand-in is worth about 100k at level 56, with highest quality, you might squeeze out 120. The average levequest is also worth 120k, with a double bonus for HQ, making it 240k. The GC hand-ins, which can be done only once per day, can range from anywhere up to 1.6 million XP for a starred HQ hand-in.

So, yeah. While you can do tons of blue scrip hand-ins, you'd have to craft a significantly larger number of items to pull this off, so it's only for those who have a lot of gil or materials to throw away.

Note I attempted to HQ each getting the 300% XP bonus.

A minor correction, HQ hand-ins are worth double, not triple. This was reduced long before Heavensward was released, and the base experience for the leves increased at the same time to compensate.

[CookieMonsta]

Sadly, this is almost the single most inefficient means of leveling up as well. The average collectible hand-in is worth about 100k at level 56, with highest quality, you might squeeze out 120. The average levequest is also worth 120k, with a double bonus for HQ, making it 240k. The GC hand-ins, which can be done only once per day, can range from anywhere up to 1.6 million XP for a starred HQ hand-in.

Blue Scrip turnins are not that bad. It depends on your timing.
The most efficient way to level 50-60 is to hone in on the cheapo recipes that appear in both the Leve and Rowena. Now, I understand not all classes have this equivalent but an example would be Mythrite Patas for BSM or Marron Glace for CUL. You craft/gather/buy a whole bunch of the raw mats. You then attempt to HQ every Pata, if you succeed in getting the HQ bar full then you turn off the collectible synthesis and let it HQ if you get part of the way then collect it for Rowena. This way, nothing is wasted.