Thier is a HUGE difference between "story line games" which are called MILSIM's and regular skirmish's like you would see in COD.
MILSIM stands for Military Simulation and designed to recreate the Military experience. These are for guys who have a decent amount of airsoft experience and the guns and kit to go along with it. Usually these games require a decent amount of equipment for you to sustain yourself for the duration of the game. As a newbie, these probably arent for you.
Try to find a local forum if at all possible, or check the regional sections here for local groups. Short and quick games and skirmishes are much better to get your self some playing experience. As you gain experience you can see what style of playing suits you best and branch out as needed.