I am traveling with 3 friends on Grand Princess leaving May 18. I seem to be the only one who has "formal" wear. ( we are broke students

The two girls that are going with have pantsuits, but no evening gowns. Princess' website says that pantsuits are acceptable on the "smart casual" evenings, but it suggests evening gowns on formal nights for ladies. I traveled on Carnival Destiny back in Dec. 99, but can't recall how people dressed on those formal evenings.. Anyone have any ideas??