I never quite understood how to level up weapons. is it just the amount of items you craft that gets your score up every life? I thought it was forge level but I still craft weapons with only 2 upgrade slots at level 5 so now I am unsure.
it's simply forging a ton of same weapon that have the skill, and the weapon with specified skill and has more than 2 enchantments need to enchanted with any scraps that have that specified skill.
instance:
scorching sword lvl 1 flame arrow enchanted with 2 scorching sword scraps will be lvl 3 flame arrow.
you must break that lvl 3 enchanted sword and that be lvl 2 scrap.
have new scorching sword with lvl 1 flame arrow and enchant it with lvl 2 flame arrow scrap and lvl 1 flame arrow scrap.
you now have lvl 4 flame arrow and repeat recycle.
god this grinding is just stupid.
the question asked was different I think, you explained how to level up skills, not weapons, there are no weapon levels technically, you have weapon tiers, the weapon you get, as I already explained in another post, is determined by the material stats, mass determines phisical attack, magic determines magic attack, and the third stat I don't remember the name of determines durability and max enhacement level, I think it was tenacity or something along those lines, it is also explained near the start of the game, one of the first memory books you find explains it, it may be hard to remember since immediately after reading it you get the boobjob from Doroelle,
still the idea is that better materials are more durable and as such hold more enhacements, forge level seems to have an effect on that as well, as I got low quality weapons with 3 enhance slots instead of 1, but we are talking about endgame level forging, for more slots you need better materials, also to get skills up you can a use the sword shrines in the dungeons, if you have a weapon with only one skill it will guarantee a level up on that one,
scrap seems to halve the level of the skill, or around halve, as level 10 becomes 6, if you want more enhacements you need to make the weapon with better materials and add scraps after most of the time, scrap does retain some stats so it is better than girl weapon materials stat wise but it is still better to use stuff like silver and steel, it also gives higher durability,
after a bit, if you save the catgirl, you can buy scrap from her and it usually has at least a couple level 2 or 3 skills on it, even the girl weapon ones, sadly you do need some good material to start but by using the skill method explained in the above post you can get a lot more out of your weapons as the upgraded skills have higher damage multiplier and sometimes even hit counts, the lady knight skill goes from 3 hits at 70% damage to 5 at 150% so it is definitely wort it