Here are some useful advices for best start in the GetsuFumaDen: Undying Moon game.
The game isn’t really complicated as a whole imo, it’s just the skills can confuse you at first.
When you start out all your skills are locked, for every weapon/sub weapon.
What you need to do is during your run sometimes you can find warps to shop areas. In those areas there is a “smithing” shrine maiden where you can upgrade the skills of weapons/subs you have unlocked.
Since you lose materials on death (or a big % of them once you get a secret art to keep some mats on death) you always want to upgrade 1 or 2 skills on them every other stage, they also appear after every boss clear before you choose your warp.
Anyway, once you unlock a skill they’re -Always- available, forever. However what you always pay for every run is to -Activate- the skill, which only uses souls. This is why you might feel loot weapons be insanely stronger than your starting weapons. Because loot weapons have random skills already activated for free while also being higher rarity possibly (the higher the rarity the higher the base stats).
Once you have skills unlocked your starting “trash” katana can have like stage 4 level stats just on the 2nd stage if you get lucky with soul drops and activate all it’s attack skills.