Need help building a deck (MTG)?

You have way too many very high mana cost creatures without any low cost ones. This is called bad mana curve and is very difficult to win with. I suggest going White or Black instead of both and getting a lot of lower mana cost creatures. Cards like Underworld Dreams is only good in a mono black deck as it costs 3 black mana to play which means that for the first 3 turns, all you will be able to play is black mana to get it out quickly (which you want btw).