Enjoy Florence to its fullest, but also make sure to do a few day trips out to the Tuscany countryside and Cinque Terre.
Both of these take the whole day. The guides are a lot of fun, you'll get amazing views, and leave with memories.
When in Florence, eat Florentine steak, schiacciata, cantuccini, papardelle al cinghiale, biscotti, and so much more.