Well, lucky for you, if you focus some of your card purchasing on the current Innistrad block, vampires are a fairly powerful black/red aggro tribal right now. Alternately, if you wait the the 29th/30th, you can go to a prerelease for Return to Ravnica (the next set, and set 1 in a new block) and play the Rakdos Guild. They are red/black aggro in every way.
Of course, this does depend on if you want to start playing in tournaments and such. If you do plan on playing tournaments in the near future, disregard Lava Axe, Llanowar Elves (which is green anyway, don't know why he put that there), and Fireball, since those are all going to be rotated OUT of standard (the most commonly played tourney format) on October 5th. Most game stores won't even be carrying M12 anymore (where these cards come from) since M13 has been about for a few months.
If you have a FLGS (Friendly Local Game Store), see if they have any new player events, such as deck building events. Even if they don't, try to find out when they do host Magic events and go to a couple. At least some of the players will be willing to give you a hand and get you started.
Since you're just getting into the game, I would recommend tracking down a Deckbuilder's Toolkit. This is a box of 285 semi-randomized cards + 4 boosters for $20. It will also give you enough land to build pretty much any color combo decks you want. You might also consider picking up the Krenko's Mob intro pack. It's mostly Red, and it is definitely aggro (cheap creatures and spells). Between those two products, you'll get a good start on learning to play.
