Flight
Flying into Rome is one of the more cost effective options that does have direct flights. This airport is a 1hr 36 minutes train ride away from Florence or a 55 minute flight. There is only 1 direct train from the airport. I suggest staying a night or two and taking the train from Rome Termini to Firenze S.M. Novella with many direct train times.
Flight
Flying into Milan is one of the more cost effective options that does have direct flights. I suggest staying a night or two and taking the train from Milano Centrale to Firenze S.M. Novella with many direct train times.
Train
Direct train options from Leonardo da Vinci-Fiumicino Airport to Firenze Santa Maria Novella run at 1:53PM - other train options will have transfers but run regularly. If you would like to rest after a long flight and stay a night or two in Rome, there are regularly scheduled direct trains from Leonardo da Vinci-Fiumicino Airport to Roma Termini; the center of Rome. Once you have rested and are ready for the journey to Florence, there are non-stop trains that leave from Roma Termini to Firenze S.M. Novella nearly every 30 minutes. "Fiumicino Airport to Firenze S.M. Novella" (no transfer) travel time : 2hr.18m, €69 "Fiumicino Airport to Firenze S.M. Novella" (with transfers) travel time : between 2.5-5hr, €31,50 "Fiumicino Airport to Rome Termini" travel time : 32m, €14 "Rome Termini to Firenze S.M. Novella" (no transfer) travel time : 1hr.35m, €30
Train
From Milano Centrale to Firenze SM Novello, it takes approximately 2 hours on a direct train. The cost per ticket ranges from 46,00 - 59,00 Euros.
Rental Car
Rental car option that you are able to pick up directly from the airport. Price is around €166/day, but does have larger sedan options.