For getting off the ground, I'd say Charlotte and Yoko are good candidates. Charlotte levels up by absorbing enemy spells (she has infinite chances to do so with each enemy, as opposed to having to get lucky when they die), and Yoko only has 3 spells.
Use either of them to unlock the stages, then you can just farm chests with whoever else. And be thankful for the offline co-op. It'll make "survival grinding" 100 times easier.
Survival Mode in theory is you and someone else getting thrown into Gergoth's room and having to duel each other, but in practice it's probably the most commonly used way to level up the grind characters (such as the Belmonts and Shanoa) by turning Gergoth into a pin cushion over and over. On 360 you have to do it online with someone else, but PS3 users can just do it by themselves if they have two controllers. At least I assume they can.
And you may find this site useful. It has drop lists for each boss and purple chest.
http://alternateharmony.proboards.com/index.cgi?board=drop
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A runabout! I'll steal it! NO ONE WILL EVER KNOW!