Firstly, its .177 and .22! A two and a quarter inch diameter lump of lead won't go far from an air pistol!
What do you want to do? If its knock tin cans over then .22 is fun. Targets get better results with .177, the pellets are also cheaper.
There is a huge difference between rifles and pistols, and as for your budget, again what do you want to do?
Do you want a self contained or co2? Decent quality that'll last, or a cheapy that looks like a "real" gun that you can shoot Gangsta style!
Give us some more details, there are no stupid questions.
My ignore list: <Hidden information>