Airsoft.

[The Crack Fox]

Weaponry
This is a sub-machine gun, its CQB so its not full size but its perfect for your age, its got a decent FPS and a hi-cap mag.
http://gunfire.pl/product-eng-1152190032-CM035.html

Noobias's special gun - http://gunfire.pl/product-eng-1152193153-.html

I would suggest this bitch, but its a bit pricy and I think the blowback would knock you out..
http://gunfire.pl/product-eng-1152195654...Combo.html

Gear
These are your jacket/trousers, you will wear these under your tactical vest and holster, they will fit but the legs may be too long, so just roll them up or get hemming tape.
http://gunfire.pl/product-eng-1152192236...wz-93.html or http://gunfire.pl/product-eng-1152191863...dland.html whichever ones you prefer.

Now for your Jacket, this may look slightly gaf, but if you wear your tactical vest over it, it shall look better.
http://gunfire.pl/product-eng-1152190788...arpat.html

It is essential you wear gloves, it helps with grip and protection if/when your throwing Airsoft Grenades.
http://gunfire.pl/product-eng-1152191481...lack-.html

Vests are mandatory when in an airsoft battle, they keep your basic needs such as Mags, Radio's and various other needs.
http://gunfire.pl/product-eng-1152196010...Olive.html

(Or if you want to go for some spec ops shit, take this http://gunfire.pl/product-eng-1152194173...DLAND.html)

Ammunition & Other
These are high grade 0.20's perfect for the gun I have listed, these are heavier than you average 0.10's and since the gun has good FPS it will carry these further.
http://gunfire.pl/product-eng-1152190220...0-pcs.html

Wear this helmet, with these goggles and this mask for maximum protection.
http://gunfire.pl/product-eng-1152190384...-2002.html
http://gunfire.pl/product-eng-1152195210...OLIVE.html
http://gunfire.pl/product-eng-1152194714...Olive.html

This set is the set I currently have, these are a durable and good quality set of pads that help your accuracy and stability while proning/crouching, these are not needed but recommended

http://gunfire.pl/product-eng-1152193455...-pads.html

Also since that gun has Hi-cap mag of 500 BB's, Depending on how long a tournament is, I'd recommend 3-5 mags.

Heres the link to the extra magazines - http://gunfire.pl/product-eng-1152189805...-AK74.html