Fist-pumping must pay well. DJ Pauly D left a $500 tip for a waitress at Greenhouse on a $2,000 tab Thursday night. The spiky-haired reality star — who just signed a deal with 50 Cent’s G-Note label — was at the SoHo nightclub with a few friends filming scenes for his new MTV spinoff show. A spy reports to us that Pauly did more than leave the cash. “He called to follow up,” they said. “He was very sweet and wanted to make sure she was taken care of.”