Colin,
You could be forgiven for thinking it's time to reach for the virtual Flak Jacket, but rest assured, it's merely a case of running out of Cognac. (And as your musical career blossoms, you will learn to appreciate the gentle aroma of a Louis XV, as opposed to that more popular, but decidely less delightful, 'Chateau De Gorilla', an insidous nectar that would be decidedly better use as aviation fuel, but instead, sadly, is the staple 'creativity aid' of many a musical aspirant.)
I'm not going to light another fire here, so STRICTLY as a personal opinion, based on my own modest experiences, Paul has given you good advice. I remember at 17, it being pretty tough not knowing which information to treat as a priority, simply because i didn't know at that stage which info WAS a priority. (And even then i chased a coupple of red herrings...)
And there could be another 'enthusiastic' discussion here about the merits of a formal education versus the 'free spirited' approach. So again, from my personal viewpoint, it could be worth you considering extra tuition or study in musical theory, including Harmony, Counterpoint, Composition and Orchestration. You might not be at the stage of absorbing this information just yet, but the theory of music, and intense study of it, has saved me a lot of time trying to figure things out, and write what i actually want to.
I don't know which direction you'd like to pursue as a musical journey, but if it's film, then there is an old adage that roughly translates as:
If you want to write concert music, study the Europeans, e.g. Beethoven (my personal favourite) Mozart, Bach. (Notice how most of 'em lived or worked in Austria? Dietz is very proud i'm sure.)
If you want to write film music, then a good place to start is the 'Russians.'
Rimsky-Korsakov, Khachaturian, Tchaikovsky, Shostakovich, and the great Borodin, just for starters.
And learning to read music well with notation for all the orchestral instruments, will give you an important tool to use when studying scores, a useful occupation i have found particularly helpful in the last 30 years. Listening to the music and reading the score at the same time, opens many doors in the skull, as you realise exactly what it is and WHY it happens.
This a rough and ready rule with exceptions, but it has some merit. (IMHO)
As you go along your particular road, please ask if you have questions. Despite the fact that we've run out of Virtual Cognac AGAIN, (I blame Michi. Since he took over the bar, things have been hell.) there is a wealth of experience here that can help, not only from us crusty middle aged farts, who still like working with parchment, but younger chaps too, with considerable abiility in mixing, sound sculpting, sample manipulation, and the digital aspects of musical production, in addition to their own performance skills. (Some of these crusty farts are pretty adept at digital stuff too. Me, i still buy light bulbs by the candle.)
Now, I'm off to see if that Michi fellow is asleep under a stool somewhere, after giving OUR Cognac a serious tasting.
Regards, and the very best of luck to you Colin,
Alex.
p.s. Some reference books that may help you, possibly now depending on your current standard, but defintely useful in the future as your skills mature.
Principles of Orchestration...............Rimsky-Korsakov.
Treatise on Instrumentation............Berlioz and Strauss. (That's Richard Strauss, not Johan, or the myriad other Straussettes.)
Instrumentation and Orchestration.....Blatter.