I would avoid the Yak's and La's, especially at first. Really small ammo load, and really not a whole lot of learning potential I feel (especially with the Yak's, in 6 years of play, I never felt like saying 'wow, that guy could made his yak fly backwards if he wanted!")
Try the P-38 (or the 110, if you're a man who likes a challenge), since it has a very generous ammount of ammunition, so you can spend enough time in the air to get a feel.
If you're interested in smaller, more nimble fighters, then once you get the hang of the nose guns, I would recomend the 109. Lots of potential for growth there, various models that have various combinations of traits, and it will make you learn fire dicipline and how to make crossing shots.
Lala is about the same or better, but its stalls just seem nastier. Amunition is also a bit of a problem since the balistics on the 20mm's are, frankly, rather crappy. Used to fly one, but after a while, it just gets boring.
Or maybe even try the P-39 once you're used to the nose guns. Not a very common fighter in the MA's, but theres a few sticks out there that will have you chasing your own tail in it.