If looking like you just went on a Hamptons shopping spree is high on your list, you’re in the right place. Because few things hit better than breezy, coastal dresses that offer an instantly polished look — no weekend getaway required. But what’s better than a one-and-done silhouette that works for a Montauk escape and an antique-shopping stroll alike? A slew of affordable picks. I found 17 chic, billowy dresses at Walmart, ranging from tiered m…