For a city experience, it's best to walk between the sights to fully experience Rome's charm. Taxis are available, but can be expensive and may have trouble navigating the city's narrow streets. Consider buying a day pass for the metro if you feel overwhelmed by the distance of some attractions, it costs €7 and can be purchased at any metro station.
If you have more time, consider spending an additional day exploring the Roman Forum & Palatine Hill or the charming streets of Monti. If you have less time, skip the Pantheon and head straight to the Trevi Fountain. Remember to dress modestly when visiting any religious sites and keep your shoulders and knees covered.