I haven't gotten to unlock the newer areas (the ones with stars) on my last play but you can go through paths with the Sun or Moon symbol by entering them on the appropriate time be it Day or Night. Also don't underestimate Monica's bracelet since it was probably the strongest weapon on my last play (which I didn't finish). Just remember splitting the Fruit of Edens evenly between Max and Monica, and also note that there is a GLITCH on the future valley area. Consider checking the board FAQ on Dark Cloud 2's message board since it lists some of the glitches you may be wary of.
So anyway I've also started DC2 again today since I'm done with DW5: Empires and God Hand. Time to take pictures! Oh and you might wanna check DC2's weapon FAQ. It lists the most efficient way of synthesizing weapons on it's "Weapon Recipes" section which involves using cheap buyable material instead of crystals which you won't find often, at least until you unlock the crystal shop.
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...then blame it to the cabbages