Just want to go over a couple things. There's very few guides as I've only found 2. One on a wiki that only has 3 articles and one here.
1) The wiki guide will tell you to just stick with the Drake Sword without explaining why. Aside from its high attack power and stunning attack that hits all enemies, when fully upgraded it gains a 100% burn chance alongside a powerful attack that strikes randomly 4 times, particularly powerful against single opponents such as bosses.
2) Wiki guide will tell you to sell your green/red/yellow/blue etc. souls for 5k a pop to level up with and such at the start. I wouldn't personally. Later on most of your stats will end up coming from these things as level costs get higher and higher.
3) If you're struggling against the boss at the end of the Hansel and Gretel line, I've beaten him fairly early. He will nuke you once he has his buffs on (multiple 1k+ damage hits), which is precisely why you should get Dispel from Dorothy. Once he has the lightning/fire/ice aspects on, use dispel. He won't reapply these either, skipping that phase entirely.
4)
You do not have to wait to kill the Pied Piper, you can kill him the moment you meet him. After he's dead, you can trigger the lamia event once you defeat the 'cat' Knight boss at the Fort and lit the bonfire after the fight. Go back to Elma's store once you do that and it will trigger.
Warning, once you enter her store and they're done talking, immediately intercept the lamia before it reaches Elma or she will die. Do
not just stand there, it is not a cutscene.
5)
It isn't necessary to kill any of the demonic princesses, but probably advised as it is very powerful considering how early you can fight it. It was available to me after I beat the boss in the Skeleton Maze, left the area to the secret garden, then came back. Hadn't killed any of the princesses at that point. The Ring of Enduring is especially helpful for this fight as it will mitigate his Mega flare's damage to a more manageable amount when defending.
6) It isn't necessary to let the Frog Princess drain you to level 1 to get the ring, she just needs to drain you once. Every drain takes 30 levels off you. Knowing this, it's best to let her drain you when you are low level, if you can manage to reach her that early.