Before you start
Record each weapon when it enters your inventory, not when you first see its area. Keep keys and gate requirements beside the weapon name so your route does not stall halfway through a region.
Efficient collection strategy
Combine weapon pickups with Shell, fragment and dungeon routes. Fainweald is the better early sweep; Mammon weapon routes are easier once your traversal options and damage plan are established.
Missable or not?
The current launch guides agree the weapons remain collectible before New Game Plus. Still, finish the checklist before committing to the next cycle.