Scry 3, then reveal the top card of your library. Draw cards equal to that card's mana value. (To scry 3, look at the top three cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)
If a card in a player's library has {X} in its mana cost, X is considered to be 0.
If you reveal a card with mana value 0, such as a land card, you won't draw any cards. Otherwise, the card you revealed will be the first card you draw.