For your first, pick up the newest last year model you can find. Meaning, old style, but the best shape. I've had decent luck purchasing several rc cars this way, saving a lot of money.
Right now the market is flooded with Jammin X1 CRT's and Losi 8ight-T's. Either would make a great beginner truck! As the Mugen MBX6T becomes more available, you'll see the market flooded with 5t's as well.
Good luck!