Welcome to ASC and airsoft in general. For learning more about airsoft you've come to the right place.
It's a great sport, but unfortunately like many sports it costs alot to get started in, and due to liability issues is generally 18+ only. Some of the above posters were alittle harsh, but they were correct. The absolute minimum you'd need to spend for a playable airsoft gun is $200 and that'd be bargain basement. A decent gun would run $300-$400, a good gun would be $600-$700, with some highly upgraded guns going for $1000 or more.
As you can see from the above (very rough) prices, airsoft is not a cheap sport. It's generally accepted that the absolute minimum you need to get into it is $500, and it's usually more like $1000-$1500 if you go with quality gear. I've seen a few people do it for less then $500, but it takes a fair bit of time, effort and jury-rigging. And of course quality tends to be a problem at that level.
If you're 18 years old or older then I highly recommend getting age verified. That will give you access to restricted sections of this forum, including the sales threads, which will definitely help in getting the most bang for your buck, both knowing what to buy and actually finding it at a decent price.
If you're not 18 years old yet don't sweat it, just be patient, save your money and learn. That way you will be prepared to join the sport once you're old enough. If you are over 18 but don't have the kind of budget I mentioned above then depending on where exactly you live you may be able to arrange to rent/borrow guns and gear until you're able to afford your own.
My baby, CA M15A4 Tactical Carbine with m203 grenade launcher, red dot sight and taclight
(total cost = ~$1000):
Me in my full primary kit
(total cost including the guns and a few things you can't see in the pic due to angle = ~$2500):