2 days — City only
Day 1: Archaeological Museum + Spaccanapoli + pizza pilgrimage. Day 2: Naples Underground + Cappella Sansevero + waterfront. Two days covers essential Naples.
3-4 days — City + Pompeii
Add: day trip to Pompeii (or Herculaneum — less crowded, better preserved). A day for the Amalfi Coast (Positano/Ravello by SITA bus or boat).
5-7 days — Full Campania
Add: Capri (day trip), Herculaneum, Procida island, Caserta Royal Palace. Naples as a week-long base covers the entire region without changing hotels.
7+ days — Deep immersion
Add: Ischia (2 nights), Sorrento, Paestum Greek temples, a pizza-making class. Campania has enough for 2 weeks easily.
Our recommendation: 3-4 days (Naples + Pompeii + 1 day Amalfi)
The Archaeological Museum is ESSENTIAL before Pompeii — the best artefacts are in Naples, not at the site.