Bro don't listen to 'guys' tryin to sell you gear down the gym most of them don't know sh*t and will give you crap advice.
First off you're still too young, by using gear at 19 you could trigger off a host of nasty side-effects, wait a year or two until you have finished growing. Get at least a year of solid consistant training under your belt before considering juice
Naposim is a brand of Dianabol (D-bol), which will pack on a good amount of weight. However I wouldn't advise a first timer to do an oral-only cycle you will lose most of your gains.
Many first timers will shy away from injectables because they are a afraid of needles etc but in reality injectables are easier on the liver as they are less toxic than oral steroids.
If you're still adamant that you're goin to juice I can't stop you so the safest and most productive thing to do would be to add a Test to your D-bol, Test Enanthate being the most preferable. If you do go with d-bol, make sure you have liver protectors,
Milk Thistle and ALA, and make sure you have some Clomid for your post-
cycle therapy.
I can't help you any more because you haven't posted your stats or your training history. Make sure you have a solid diet in order or the money you spend on steroids will be a waste.
Don't rush into anything bro, you are still young, there is plenty more natural gains to be made at 19 your are a testosterone factory at your age. RESEARCH RESEARCH and RESEARCH!
Have a look at these sites before you go any further:
www.muscletalk.co.uk
www.fitnessgeared.com
www.elitefitness.com
Ask plenty of questions and get as much info as you can.
Stay safe, Jock