I started handgun shooting at age 14 with a Crosman 600 CO2 pistol. That was nearly fifty years ago, it taught me a lot about basic handgun skills once I was able to buy a cartridge handgun.
Don't have any specific air pistol recommendations at present but there are lots of models available over a wide price range. They are fairly cheap to shoot, and generally legal to purchase and own for people your age.
Also, see what is available from local gun clubs. They may have a junior shooters' program which can provide instruction and the use of club-owned firearms.
Obviously a course in firearms safety should be your first priority.
Best wishes for an enjoyable experience in competition shooting,