IT’S the golden age of budget shopping when an Andrew Jackson will get you a necklace, a miniskirt or anything from Miley Cyrus & Max Azria, the Disney princess’ new line at Wal-Mart. There’s nothing you can’t buy with $20 and a smile these days in Manhattan. From the well-stocked Topshop sale racks to full-priced finds at Mango and Forever 21, here are some of our favorite bargains.