I used to go 3 or 4 times a year. It was for work, but then I would tack on some vacation days at the end.
General advice: Don't book a cheap flight to Europe, hoping to get a $50 flight to where you want to go. Book both together. It is like getting a cheap flight in the US. They are available, but the second you count on one, they aren't there. Leave more time for being at the connecting airport than for inside America. Think Chicago O'hare, only more spread out. Also, you really don't want to be in a foreign country without your luggage.
Also, consider a train. No guarantees that it will work out cheaper, especially if you only plan on seeing your friend and not exploring also. But if you do plan on exploring, a Eurorail pass is wonderful. Also, train and plane stations are usually together.
Ask your friend about when everyone will be on vacation. I seem to remember Italy is one of the countries where everyone goes on vacation for the same week. I know at one time they had to make a law that bakeries couldn't close during vacation week, because otherwise tourists would starve.
Where you going? The Naples Museum and the Vatican Museum are 2 of my 5 favorite museums. But then, I like Ancient Rome.