I haven’t been to Gibraltar but I would never skip going ashore there. I really liked Cadiz, just walking around. Pisa is not just the tower but are the church and baptistry. There are other places to visit there. However from that stop you could visit Florence instead ( or in addition to Pisa ). In Florence, no need to go into the major art museums - the Duomo museum is rather small but has the original baptistry doors ( amazing ! ) as well as a Michelangelo statue. Also the Piazza della Signoria has 3 excellent original statues as well as a copy of David. Santa Croce church has the amazing graves of famous Italians such as Galileo.