If you are short on time and want to take a lot in, Naples Sightseeing Buses are a good alternative. Here a few good options:
The UNICOCAMPANIA 3T is a great way to get around Naples and Campania. At just €20,00 for 3 days it is valid for travel on all public transportation in the Campania Region. That includes the Alibus Airport Shuttle, the EAVBUS to Vesuvius, and local buses on the Islands of Ischia and Procida.