What to sell, auction and/or sacrifce

Greetings! I've been playing Dark Summonor for a few weeks now and I'm still trying to figure things out. Right now I'm trying to figure out what's worth keeping (and levelng), what's worth sacrificing and what's worth trading/selling.. (As a point of reference, I've put together a spreadsheet of *most* of the monsters I have in my possession currently and I need to decide what to do with them soon.

That spreadsheet can be located here.

I would really appreciate someone pointing the way and helping to educate me a little in what is worth keeping and what isn't.