To make the most of your day in Florence/Pisa, it's recommended to hire a private driver or take a guided tour. This way you can maximize your time on the road and don't have to worry about public transit schedules or getting lost. Depending on your budget, prices can range from $200-$500.
If you have more time, consider visiting the Florence Duomo or Santa Croce, two of Florence's most famous landmarks. If you have less time, consider skipping Palazzo Pitti or Ponte Vecchio. Don't forget to wear comfortable shoes as there will be a lot of walking involved. And finally, don't hesitate to try the local cuisine, including the famous Florentine steak and Tuscan wine.