Is this itinerary do-able?? Paris 2 days, travel to Santa margherita (2 days), Tuscany (3 days), Rome (2 days). I am not sure how to get from Paris to Santa Margherita???
Forgive my ignorance, but I don't know where Santa Margherita is. But if this is your first time in Paris, I think you definitely need to spend 4 days there and skip the other town -- then head to Tuscany and Rome.
I believe the only low-cost flight out of Paris to Italy, on EasyJet, goes to Milan. (cost is approx $50) From there you may choose to connect to Florence by air or train. I'm doing this in September. You can fly directly to Florence from Paris on other airlines, but they are not low cost.
You can also get cheap flights from Paris to Venice and Rome =)