Sixgun,
I know exactly how you feel, as I was in the same position, although when I started there weren't so many practice missions.
Ask people in my squad and they will tell you how I used to complain about having bent gun barrels, a giant target painted on my magnetic plane, and the ground crew loaded my plane with blanks. But eventually I got better and better, and after a little more than a year I reached level 31 (MORAF).
There is some great advice above, but I would also say that in the beginning you will get your butt beat, and there are some top players with no heart that have no problem beating you down, but don't let that upset you. Keep playing, keep learning, and never quit. Even if you lose a game you still get points and it doesn't count against your wins, or stats, so don't worry about being on the losing team.
After a while you'll have enough to upgrade or buy a new plane. The way I did it was just upgrading my basic plane to start, then when I had the money I bought the following planes in order:
German ~ Albatros D.III, Albatros D.V, Siemens Schuckert IV
Allied ~ Spad XIII, SE5A, Sopwith Camel F.1
If I was to do it again, I possibly would skip the Abatros D.III, and the Spad XIII. Also, even after purchasing the top planes (Siemens, and Camel), I still played with the other planes until I was able to fully upgrade the top planes.
Expect to get shot down a LOT at the start, but never get mad. You may get frustrated, but don't let them get to you, and NEVER use any profanity, keep the game clean. There are people from all over the world, and kids playing, so we need to keep it clean in the chat, in the game, and here on the forum.
Best of luck, remember you will get better as long as you don't quit.