The little black dress, simple black pumps, denim—some styles are always on trend, no matter the season. The key to having a popular boutique inventory is mixing these versatile pieces alongside trendier garments that highlight the fashion of the region and season. Your customers will love the range and have the ability to build complete, balanced outfits after visiting your boutique. A White Button-Up  Whether it's being dressed up with a blazer for a dream-job interview or accented simply with dark denim and black flats, the white button-up is a true must-have for your customers because of its versatility alone. A Black Blazer Don't underestimate the neutral-hued blazer. We love how a tailored jacket makes a vintage-inspired graphic band tee look a bit smarter—or...