If you want to give your credit card some exercise, head out to Nathan Road Shopping District in Yau Tsim Mong. It's also full of great shops and restaurants, so you can spend the afternoon having a wander. Splash some more cash at Langham Place Mall, Mong Kok Computer Centre, and Ladies' Market.
If you want to give your credit card some exercise, head out to Harbour City in Tsim Sha Tsui. Why not take a stroll along the port and watch the sunset while you're here? Splash some more cash at Canton Road, Chungking Mansions, and K11 Art Mall.