From my experience, Italy is way more enjoyable if you slow down and don’t try to cover too many cities. Pick a few and really explore them; book major attractions like the Colosseum or Vatican in advance to avoid crazy lines, carry some cash since smaller places still prefer it, and always validate train tickets to avoid fines. Also, eat where locals eat (slightly away from tourist spots) for better food and prices, dress modestly when visiting churches, and be mindful of pickpockets in crowded areas like Rome or Venice.