Ok, here below there are my advices!!
Venice (2 DAYS)
- PIAZZA SAN MARCO
- ST, MARK'S BASILICA
- CAMPANILE
- MUSEO CORREL
Milan (2DAYS)
- PIAZZA DEL DUOMO
- MUSEO OF DUOMO
- GALLERIA VITTORIO EMANUELE II
- PALAZZO REALE
Florence (3-4 DAYS)
- PIAZZA DEL DUOMO
- UFIZZI GALLERY
- GALLERIA DELL'ACCADEMIA
- PALAZZO PITTI
- MUSEUM OF SAN MARCO
- PONTE VECCHIO
Rome (4 DAYS)
- THE COLOSSEUM
- PIAZZA CAMPIDOGLIO
- FORUMS
- THE PANTHEON
- VATICAN
Naples (3 DAYS)
- EVERYTHING!!!!!!!!!!!!!!!
- CAPRI AND ISCHIA
You need at least 14 days for visiting those cities and you better travel by train around THE COUNTRY!!
Bring at least Euro 2000 for hotels, thickets and restaurants, SHOPPING NOT INCLUDED!
Let me know if you need more tips about it and I'll be more than happy to help u out!
My best,
Giuseppe Russo