I am planning to fly from Florence, Italy-Paris, France (CDG). The most affordable flight that I've found arrives at 2:35 pm and my transatlantic flight is at 5:00 PM.

Earlier flights are very expensive unless I fly from Pisa-Paris (Orly or Beauvais).

How early should I aim to be there? airFrance will not work with me to connect the flights so I could just go to my terminal.