hey hey scubakitty727
best and cheapest doesn't always match what you're hoping for. you're in high summer season with many cruises arriving and departing from civitavecchia. how many ships will be at the port that day, how many on board could be 10,000 to 20,000 passengers, wanting to do the same thing as you. coming in from rome is about an hour half+ on a full train, where it drops you off as frank says with walking, how long are lines to get on shuttle, how important is waiting and stress for you, how many grumpy/pushy/impatient people are trying to get on ship. been there done that.
we were registered with cruisecritic.com , found roll call for our ship, posted who wanted to share taxi and within minutes had 4 of us to share coast, was fabulous. the taxi was 130E split 4 ways and was dropped off right at terminal platform.
the cost was not an issue since shared and spending $$$$ on cruise, airfare and rome stay made up for it.
i know many want cheap/budget/reasonable ways nowdays but things are expensive everywhere, we dealt with it and was happy with our decision. it's your option and pocket book, have a great cruise and enjoy.
aloha