You'll find the Gossip wandering around the eastern part of the Temple Quarter. When you track her down, ask her, "Have you heard news of a witcher in town?" and then tell her, "He fancies women with or without magical abilities." The Gossip will randomly respond in one of three ways. You're looking for the response where you'll get to introduce yourself, and where the Gossip will ask for a present. If you get one of the other responses, then just keep trying.

When the Gossip asks for a present, you'll be given two choices: "some sort of frock" or "a precious stone." However, the Gossip is very particular in her desires. If you give her the wrong item, then she'll decline it, but she'll give you a clue about what she's really looking for -- Gold Women's Gloves or a Diamond. When you finally manage to give the Gossip what she wants, then she'll give you what you want.

Note: You can buy Gold Women's Gloves from the peddler on Merchant Street. You can buy a Diamond from Leuvaarden. You can also win a Diamond from Zoltan Chivay by playing the drinking game with him, but only if you didn't already win it in Chapter I.