After departing the Met Gala steps on Monday night, all bets were off on where to find the night’s VIPs next. While private parties were a sure bet for some of the biggest names (Beyoncé Knowles-Carter), the spread-out after party options for the rest of the crowd meant that you never knew when the party would really get started — or who would show up. As one of the classic “after” haunts, Boom at the Standard, High Line attracted an early crowd that included designer Christian Siriano, Coco Rocha, Tommy Dorfman, artist Dustin Yellin and Danai Gurira, as Samantha Ronson kicked off the vibes behind the DJ booth. After Questlove swapped in for his set, Ronson had the entire sunken VIP section to herself, but the night was still young — it wasn’t even midnight yet. Gabriela Hearst , who hosted the party alongside her Met Gala date Grace Gummer , arrived ready to celebrate.…