I'd suggest holding off on your first purchase. Instead get out to a game in your area and rent. Meet with local players and learn first hand about the various guns they use, ask questions (politely) and if your nice some might even let you handle / fire their airsoft.
As well, many local games will have an Age verifier at the game and will allow you to get the age verification out of the way. Thus allowing you to check out the classifies which in turn will open many different options.