This site's main objective is to help you gain information about decks you've already built. Once you've put in a deck, it will give you information on your land distribution, mana curve, color ratios, creatures to non-creature spells ratio, essentially whatever you like. It can also suggest great cards to add automatically, and, if you've got more time, you can submit the deck for others to give feedback. Even if you don't have a complete deck designed yet, you can submit a partial deck for feedback, or even just ask about an idea you have in the forums. You have lots of support for building and refining a deck idea, but, the initial idea for the deck will probably have to come from you. That would be a cool feature, though: put in your collection and see decks that you can build or nearly build. I bet someone, somewhere has built a site that does that, but I don't know where that would be.