Most of the sites mentioned are walkable, but consider getting a fast-track ticket at each location to avoid heavy crowds. Taxis aren't affordable, so try using the metro, bus, or tram to get around, which is cheap (1.50€ per ticket, valid for 100 minutes) and efficient. Rome is bicycle-friendly, and renting a bike for about €4 per hour is a beautiful way to discover the city.
If you have an extra day, take a day trip to the beach at Ostia, Florence, or Pompeii. In contrast, if you are short on time, prioritize sites or group sites close to each other. On Mondays, some sites are closed, so plan accordingly. Wear comfortable shoes, clothing, and sunscreen during summer months, and drink plenty of fluids to stay hydrated while exploring Rome's beautiful treasures.