[PS2] Odin Sphere - Hot sex from Atlus

This game is incredibly hard and I'm obviously doing something wrong. The awfully restrictive item management doesn't help, either. I really want to continue playing, but it feels like I'm stranded without some expert advice.

I'm currently unable to beat the Forest Witch (second boss for Gwendolyn). I tried it countless times already but don't even feel like having a chance. Sometimes I manage to take away half her HP, but then she totally crushes me with her fire and poison spells. I've got enough antidotes, but using any item renders you totally defenseless in that battle.

The whole concept of growing plants and fruits and mixing stuff seems really deep, but there's only so much information I'm able to make use of in the game at one time. Furthermore, I'm constantly out of item space and still have no idea what's worth keeping. I guess this is a major detriment to my progress and don't know how to avoid being stuck with nothing but useless junk.

I figured replaying the first chapter was going to help me stock up on some useful healing items, but then I noticed that there seems to be no option to replay an already completed chapter/dungeon. If this turns out to be the case, I can't help but say I'm stuck with no other option than to restart the game all over from the beginning.

Someone please help me out of this dilemma and show me how to enjoy this game without wading through tons of FAQs and Walkthroughs.

How ya doing, buddy?