For an ensemble that's very simple but can be modified in a myriad of different ways, dress in a dark green horizontal striped crew-neck sweater and chinos. A pair of dark brown athletic shoes easily boosts the street cred of your ensemble. Perfect to show the world that even as a teen you can make your own style choices.
For an ensemble that's worthy of a modern style-conscious man and casually smart, try pairing a beige shirt jacket with chinos. Take an otherwise sober getup down a whole other path by finishing with a pair of dark brown athletic shoes. Men who are curious how to sport modern off-duty dressing as you make your way through your teenage years, this combo should answer your question.