I feel that it is my job to give you guys some advice on training, and tell you what I would do if I were 16-17 again and hardcore into soccer, trying to break into a professional level squad. I can really only speak as a midfield or attacking player.
There are lots of things you can work on to make your game really, really good. Three things, vision (awareness of the game around you), technical skill (not natural ability, but learned, practiced skills), and fitness/stamina are what really counts in the total player. Having "natural" talent of course helps, if you're lucky enough to have it.
Aerial passing, crossing, lobbing, etc... one of the biggest things missing in most competitive players. Sure they can dribble all day and maybe even have a shot or a crisp pass on the ground, but I see that there's a serious lack of players in the norther part of our continent (Canada and the US) that have the combination of vision and technical ability to be a real threat to defenses on the field from anywhere. In this area technically, I would work on your softer kicking touch. Making accurate aerial crosses from inside or just outside the 18 box, putting a ball INTO the 18 box from outside of it (in the air) etc.... work on putting some backspin on your lobs and through balls, so that an attacker can get to your pass without running out of options.... that's what I'm talking about when I say vision...knowing what kind of ball to provide, and knowing when to put what ball in. It's not terribly exciting to practice this stuff, but if you get good enough at it, you'll be creating chances for your team, and for yourself as well.
Another great thing you can do to learn a better vision of the game and make yourself a more valuable player is to watch games.... watch games that are in your level, ones that are above AND below your level. If possible, watch from a distance, and from up high.. you will start seeing moves that can be started, passes that should have been made, and open spaces that should have been taken advantage of. It seems silly, but think about what you would do in whatever situation you just saw. In your head, think about if you were the guy with the ball, or if you were the one hoping to get the cross or the layoff to get a shot. You can learn a lot by watching any soccer game, and if you see enough of it, I have a feeling it gradually sinks in and becomes second nature to look for the right play when the right time comes, and that makes you a very valuable player.
I would also work on your natural strike... your shot. I and many other people have posted a lot of info on taking a good shot, but I've become more and more aware as the games go by that it's more important to work on shots you don't normally practice in the backyard. You can dead ball all you want, and get really good at it, but I find that in the real games, most of my shots, even from distance, are taken at full stride. Practice taking hard, low shots from distance while running; both running toward goal, and perpendicular to the goal. These kinds of strikes are extremely important, and come up more than anything for an attacking player or midfielder.
Another VERY important skill that no matter what you do or what position you play, and you can't practice very well by yourself, is heading. It's extremely important in high levels of play to be able to put power and accuracy into a headed shot from anywhere within 12 yards of the goal frame. You need to be able to flick-on with your head, make surprise passes with your head, and of course, shoot with your head. Working on the angles comes first, and then working on transferring the power from the ball into your headed shot comes second. You're going to have to practice with a friend who has a decent kick... and you're going to have to get used to being hit in the face, getting a little dizzy, and maybe getting a black eye or two if you're not already very proficient at heading the ball.
Definitely not least, you need to have top physical fitness to be as good at the end of the game as you are at the beginning. This is my big shortfall, being 30 and only in "decent" shape.. fortunately in my rec leagues we can sub on the fly, so it's not a huge deal, but when you're out there and you can only make two or three really hard runs before you lose some of your will to live, it's not going to impress any scouts out there, or any tryout coaches.
You need to be in top shape all year..swimming, running, lifting weights, stretching, etc. I'm sure you've heard it a million times, but it's SO important. I'm not a doctor, and I don't know you personally, but it seems that you're old enough that you can fully work your muscles without suffering any of the negative effects of weight lifting at too young an age. I've found that doing a lot of leg, ankle, and abdomen strengthening exercises will really, really help out your technique and your overall game. DON'T underestimate abdominals, obliques, and your back. I personally don't just do crunches, I actually do weights and resistance training to really build those muscles. You will not regret it. You can have the strongest arms on the field, but the guy with the leg strength and the trunk strength is going to muscle you off the ball every time. I don't know your size.. I'm 6'2 240lbs so I don't have much problem muscling people off the ball, but your situation might be different. Be as fast/quick as you want, but if you're not strong, the other guy will win the ball just about every time.
It's important of course to eat well, don't be a dummy when it comes to drinking, drugs, etc... what might seem like fun now could ruin your potential career, your life, someone else's life, etc. When you get to be my age, you really appreciate the game for what it is, and what it could be....at 16-17 I don't know if you'll have the same viewpoint, but it's something to consider. Any team is going to take a player with a really good head on his shoulders and a positive attitude about team play, and about life in general, etc.
Lastly if you really want to get into the pros, one thing you're going to have to do is APPLY. With the PDL and A-League, etc teams in North America, some of them have an open tryout day or two per season. It might cost you a bit of money but it could very well be worth it in the long run. They can tell you what to do to get on the team in no uncertain terms, they can tell you what you did and didn't do right... you might not make it your first time, but you never know! If you work on what they say, and show up next year with more skills and more reasons to have you on the team I can't see why they would shop elsewhere for a quality player!
I hope this HUGE post will give you some ideas of what I would be doing if I were in your position 13 years ago.... of course, knowing what I know now, I would do ANYTHING to move to England or another country in Europe. Why? Because that's where the best soccer on earth is, and in order to even be noticed or heck, even legal to "WORK" as a soccer player overseas is to be a proven US International. That's no easy task, and since we have such weak soccer developmental systems in North America...you get the picture. Obviously if/when you make it to the PDL level, and you get noticed, you could find your way to bigger places... MLS, etc etc.. National team, and maybe even "all the way" to the big stage in Europe...Who knows!
In the meantime, you're gonna have to get a job. I don't think players in the PDL make very much money playing soccer, and I'd be willing to bet that more than half have to take on jobs besides playing soccer (personal trainers, perhaps?). I assume you're looking into going to college for non-soccer related things... that'd be another way to get into a high level team...playing college soccer... but I have a theory (again, remember I'm just a dude on an internet message board, not a real expert) that the College Soccer setup we have going in North America is really hurting our soccer players' chances of ever making it big abroad or on the world stage. You're risking major injury, burnout, and basically 4 prime playing years for essentially nothing, soccer-career-wise. I could be wrong, but that's how I see it.