Selia Yang   New York Magazine Pick   The Collection: Chic downtown style for the spirited bride. Yang favors soft, flowing silhouettes, from stylized layered sheaths to flirty separates.   The Gown: Ruffled silk organza bustier with satin mermaid skirt.   The Price: $2,400.   Where to Buy: Gowns range from $1,200 to $6,000 and can be purchased at Selia Yang.