So the easiest way to level...

[Corkafish]

Those leves are only most efficient if you're trying to conserve leve use. If you don't care, then you're better of spamming a leve that only takes 1 item.

This is sort of true. One of the level 45 triple turn-ins for ARM requires turning in 3 chestpieces (three times of course), which use 4 Mythril Plates each. Each plate takes 2 ingots, and each ingot takes 2 ore, so 3*3*4*2*2 = 144 HQ Mythril Ore for one leve. That's a serious resource investment. But then there's another one which only requires 3 Cobalt Ingots.