54 W 21st St between Fifth and Sixth Aves. Subway: F, M to 23rd St. By appointment only. Engaged ladies on a budget should make an appointment to shop this charitable boutique’s designer gowns. The dresses—donated from other bridal boutiques and designers—are normally discounted up to 75 percent, but at this two-day event they will be an extra 35 to 50 percent off. Vera Wang strapless tulle gowns are $1,095 (retail $6,500), Angel Sanchez sweetheart-neckline styles are dipped from $3,500 to $795, and Enzoani backless mermaid dresses are $495 (normally $1,210). All proceeds are donated to organizations that aid disadvantaged children in the city.