Florence's aperitivo (18:00–21:00) often includes free buffets with drinks. 10–15€ for a glass of wine + serious food.
Best aperitivo: Caffè Gilli (elegant), Sei Divino (wine-focused), Volume (Oltrarno, alternative crowd).
Don't fill up so much you skip dinner — many tourists do this without realizing aperitivo is meant as a pre-meal.