Gear questions

[Niwashi]

You can't sell it if you've used it. It's bonded to you. Your options are to convert it to materia (if you've reached the point in the story where you learn that), dropping it, or putting it on a retainer in case they add new classes.

You can still sell to NPCs, just not to other players. (Of course, this sort of low-level gear doesn't get more than a few gil from NPC merchants, but technically you can still sell it.)