my opinion
Here's a very simple itinerary idea to start of from:
2 days exploring Florence, one centered on discovering the city and the second on museums (book the Uffizzi and Academia, ignore rest unless you are an art fanatic)
1 day go to Pisa for day trip then head to Lucca
1 day tour of the Chianti region
1 day tour of San Gimignano
move to Siena
1 day exploring Siena
1 day tour of Montalcino
1 day tour of Montepulciano
2 day tour going trough the smaller medieval cities south-ish of Florence
Don't hesitate if you got more specific questions. Keep in mind that this itinerary is going to be heavily based on personal preferences. For something more detailed and/or personalised you would have to give us a better idea of what you enjoy doing.