Use google flights as a starting point it is pretty accurate as far as airline prices and always book directly with the airline unless there is a major price difference.
Like the person before me there is no direct flight from the USA to Florence.
So you might start in Rome to get to the region of Umbria and its small hilltop towns of Orvieto Perugia, and Assissi. I am going there next week to ring in the New Year at
Umbria Winter Jazz Music Festival http://www.umbriajazz.com/
From Perugia you can use Florence as a base to explore the region Tuscany and some of its smaller towns Siena, Pisa etc.. From Florence you can take the train to base yourself in Monterosso al Mare the last town on the Cinque Terre closest to Milan, the point where you may want to fly out of.
I did the hike from Monterosso al mare to Vernazza in the evening in about an hour and a half when all the tourists were gone and got some great sunset scenery e.g. http://www.architecturaldigest.com/story/new-mediterranean-vacations-vernazza-italy-article.
Another thing there is a bike path in Umbria Assisi to Spoleto with some pretty damn good scenery
http://www.meravigliosaumbria.com/bike_path_assisi-spoleto.htm
You just have to do the research. Look at youtube.
