Margellina hotel is a youth hotel.
Ostello Aig Mergellina, Salita della Grotta, 23, 80122 Naples, Italy Map
It has private rooms and 30€ per night. You will see this hotel is near to a metro station and seaside. You can walk many great places by walking from this hotel. We
walked from hotel to Castel Nuovo, then Castel Nuovo to Palazzo Reale (Royal Palace), then Royal Palace to National Museum of Archaeology. Then while we were returning to our hotel back we visit many old places on the way. I suggest you to walk by the seaside at night.
Paradisoblanco Via Catullo, 13, 80122 Naples Campania, Italy Foursquare
You can get a great breakfast for 10€ with a great view of Naples sea and islands.
Naples traffic is very terrible. You can use bus or go by walking instead of using taxi.