Forza Motorsport 3

All the driver level achievements will be gained as you progress through the season career. Every time you finish a race you gain xp. It is best to win the race as you get more xp. You should get this around Year Two of the career mode (if you win enough races). Every time you rank up your driver you get a free car, as you progress through the career mode the gaps between levels increase but the xp for winning races also increases for the longer races. It will come it just takes time.