I have a limited understanding of this, but, early on in the game, the better weapons cost so much more to level up that it almost seems like it'd be worth levelling a beginner weapon before choosing what weapon to level.

The Healer's Staff is also kind of pointless, as I'm pretty sure that a magic boost will also make Cure heal better. I levelled it to, like, level 12, which was kind of costly, before going back for the Pearlwing, which still, where it's at now, as it is less costly to level, being 24, heals more and also gives a great Magic boost.

They say that the Belladonna Wand is the best weapon for Vanille, but it costs so much to level that I don't think that I'd be able to complete it before the end of the game, anyways. I just got to Chapter 11 and, perhaps, you score massive amounts of Gil on Pulse, but that seems kind of doubtful to me, barring that I don't complete an extensive series of sidequests.

You pretty much have to cheat and know that 36 Sturdy Bones will give you a 3X multiplier and that Crank Shafts and Superconducters give the best purchasable EXP if you're going to finish the game with your weapons not at, like, level seven.

They'll give you a canonical set of weapons to choose from, but, if you don't want to log eighty hours in this game to score enough Gil, just go with whatever gives you the best stat boost, in so far that it isn't too costly to level.