score:7
This is Firenze Card. It costs β¬50.
It gives 3-days access to most places worth to visit in Florence and to public transport.
About public transport, Firenze is not that big: everything is at walking distance, even from Santa Maria Novella train station. I wouldn't recommend to go downtown by car.
Most historical places, mainly churches, are entrance free. Some places, like the Duomo, are equipped with pay-for-light machines.