Hearthstone Debate: First card to craft?

Concider the following scenario; you just started hearthstone, you have all the basic cards unlocked and through the achievment system you now have your first 100 dust you can craft your very first rare card or two commons.

Which card or cards would you craft to give you the most overall utility to help you be more competative against all the netdecks out there and why?

Bonus round: You've picked your absolute favourite class and will play that one exclusively for a while. Which class would you pick and would this change your pick of card(s)?