I logged back to the game, but I crafted a few dupe weapons in the forge to increase my Blacksmith Ex Job's level. So far, I managed to raise it to level 2 after a few hammering. It takes time to level an Ex Job but it didn't matter much since the level is tied to your proficiency in creating high rarity items. The higher your level is, the more you can easily craft unique or even Legendary weapons. Your repair rate in weapons also increases and at higher levels, you also have a chance to use lesser materials to craft things.