In 2012, Rachel Mansur and Floriana Gavriel launched Mansur Gavriel — then a small collection of leather totes and drawstring bucket bags in a variety of colors. Almost immediately, the brand was a success: Within a month of its debut, there were already waiting lists at retailers for coming shipments and, by that fall, the bucket bag was one of the most prominent accessories on editors’ shoulders at New York Fashion Week. Since then, Mansur Gavriel has grown considerably: The designers have won two CFDA awards for accessory design and introduced footwear this past spring. Last fall, they opened their first dedicated store, a pop-up in SoHo. On Tuesday, the space will transform into a colorful candy shop, created especially for the debut of the brand’s spring/summer 2017 collection. (It will open to the public thereafter.) Next, the brand will debut women’s clothing during fashion week in September — and, with a See Now, Buy Now Model, will make it immediately available for purchase. Mansur Gavriel has done this all without traditional advertising; the brand avoids print advertisements in favor of street posters and an active Instagram feed, where they have amassed a half-million followers. “We don’t have this traditional…