How should a skinny teen boy dress?

Summer is starting soon and over the summer I want to redo most of my wardrobe. I want to dress very trendy, not just the t-shirt and jeans look that I always wear. (although I still w ould like to still wear them, just more fashionably) i'm also very intrested in formalwear, like ties. Sport coats/blazers etc. But use those elements casually enough to be able to wear it to school regularly. Now, I am very thinly built. (the scientific term I think is ectomorph) so what could I wear that still accentuates that frame?