At the very least - play one game ffs
You might end up hating it - unlikely but you might.
Also sites do vary a bit too - some are more serious & others less (safety is still high priority)
So as you have never even played - COD & Youtube will only give you a rough idea
Actually trying to play is a LOT different than you could begin to imagine
Apart from all that, you will be running around like you haven't got a clue
covered in sweat & mud plus apart from all that you will have to quickly work as a team with people you have never met before
Most of them will be quite friendly but you will experience a few to$$ers and not all people play the same way either
So with all that in mind - you will be thrown into a place of saddo's with toy guns that you have never met before
You will be expected to take your hits and call yourself out - just do it even if you are not sure & ignore the non-hitakers
Leave your ego at home and play for fun trying to enjoy yourself......
Now after your first game, if you and your parents are ok with you getting shot to $hit
(well at least you getting out for a full day of crazy exercise, trying to act responsible & mature etc...)
Then THEY could consider buying YOU a 2-tone gun at some point......
Do not under any circumstances think that you can get by with a JBBG for about £70 - £80
(you really will regret it and the resale value if it doesn't break is sweet F*ck All - but bet it breaks)
Besides the guns from a site with BB in like JustBBGuns or BBguns4less are usually very poor
(yes some guns are ok but there is a lot of crap they sell to noobs and younger first time players)
If you do eventually decide to buy - well your parents for that matter you will need to spend around £150+
a good starter gun like G&G or ICS starts at about £120+ but then you got battery/charger/mask/bb's etc.....
Some possible good decent starter packs to consider.....
http://www.fire-support.co.uk/category/starter-packs-clear-bb-gun/
or
http://airsoftzone.co.uk/airsoft-guns/starter-packs
This seems to offer good value for money plus 2 mags - not brilliant mags but 2 mags all the same....
http://www.fire-support.co.uk/product/ics-m4-commando-clear-starter-pack-aeg-airsoft-gun-set
You might be able to pick up a decent s/hand starter but you need to know what you are buying
All the same you gotta get out there, test the water to see if YOU and more importantly if your parents are ok with this
Then if you get your own gun - it is a big outlay but as long you keep it simple you can keep the ongoing costs quite low
eg: walk on fee say £25 for a game each fortnight plus a £10 bag of bb's which should see you ok for 2 or 3 full game days
so say £30 each game you play......
But deffo play a game or two before splashing out.....
Youngsters have many things going on in their lives - exams, girls, going out & growing up etc....
But if you & your family are loaded - the wtf go for it - just be careful if money is tight trying to pursue another 5 min wonder