nuttah - I see from your profile that you live in London... that is one place where there are gyms in abundance... if there is a YMCA near you go there... it is cheap and tends to have the equipment that you need (free weights). Stick around on
www.uk-muscle.co.uk as there are lots of guys onhere who know their stuff and can give you good advice.
When you do get to the gym make sure you don't just train chest - otherwise you will soon hit a barrier - your body tries to stay in proportion - so make sure you train your legs and back as well and u will see lots of size come on. Youare still very young so will e able to make a lot of progress without any chemical assistance. Best of luck.