This is just one of many mistakes people make when organizing their Italian holiday. Let's make a list of what to do and don't.
FOCUS ON ONE REGION
Italy is divided in 20 regions and each one has plenty of attractions and great food to enjoy. For example, if you want to see Rome book a 7 days (or more) stay in the are and make day trips and local tours withour losing too much time in transfers.
BOOK IN ADVANCE
Good accommodation, guides, drivers, tickets etc.. run out quickly and if you book last minute you might not find availability at all or just poor service. Two months ahead usually is enough
IF YOU DO NOT KNOW THE PLACE ASK FOR A PROFESSIONAL
You might save some money if you make some arrangements on your own, but you might lose at lot of time and miss some crucial details or hidden issues that locals are aware of. For example there might be a Metro strike and you cannot use public transportantion during your stay in Naples. Or the Pope might give mass to in the Sistine Chapel and it will be closed on a certain day.
USE PUBLIC TRANSPORTATION AND TAXIS IN CITIES, PRIVATE IN THE COUNTRYSIDE
Italian cities were not designed for cars. Streets in Rome Naples and Florence for instance are narrow. Private cars are not allowed in some areas and traffic is very common. Walking is often preferable. On the contrary in the countryside and little towns public transport is often very scarce and you have greater flexibility and opportunities with a private vehicle.