Alexander Wang’s got the hype, the retail presence and even his own celebrity stylist, model Erin Wasson. But the young designer has to show he’s more than just a flash in the pan. Enter a high-energy fall collection that was certainly a step in the right direction. Wang has a consistent vision and a strong sense of his customer, who’s a little bit gritty and molto street chic. She can pull off his trompe l’oeil silk cargo pants — made to look like trousers worn low over boxers à la K-Fed — and wear his roomy blazers, ripped denim and off-kilter tanks with a just-got-out-of-bed confidence. And she’ll toss the pretty “It” tote aside for his leather clutch, inspired by a men’s toiletry bag. But Wang has to fine-tune that message, because his dressed-down vibe hewed too closely to those of others, like Marc Jacobs’ neo-grunge affair of ’06.