I like the Druid, you can learn and cast the Pathfinding spell before you even level up.
But Death Knights and Lords are close seconds for me. Tactics for the DK, who can start with a Vampire and thus have a Phase 1 creature right off the bat (no pun intended) and a Lord with Nobility and Estates works nicely too for early income.
I'm still in favor of Lords. Money gets you what you need and want. But since I haven't really given every class a fair shake yet, I reserve the right to modify my choice.
Lord. CCGs always have a problem where you just don't get the cards you need at the beginning -- everyone who's played Magic knows the feeling of just not getting any lands and dying because you just can't play anything. Lord makes sure you have what you need early.