maybe this is helpful:
For evenings, resort casual is also appropriate (no jeans, T-shirts, shorts, or bare feet please after 6:00 PM on the ship). Cocktail dresses for women and suits or jacket and ties for men are appropriate for formal evenings (1 formal on 4 to 6-night cruises; 2 formals on 7 to 10-night cruises; 3 formals on 11 to 14-night cruises and 4 on 15-night or longer cruises).
Source: MSC Website
Following information is taken out of MSC daily programme. The original programme is kept in German so let me try to translate:
Gala: Gents - Smoking or Evening suit and tie
Ladies - Partydress or Cocktaildress, formal
Formal: Gents - Jacket and pants (but no jeans)
Ladies - informal Dress, Pants or sportive clothes
Casual: Gents - sportive shirt, long pants or jeans
Ladies: dress, Pants or sportive clothes
Shorts are only allowed in the self-service restaurant.
No undershirts, bathsuits, bathropes and barefeet are allowed at dinner time.
Maybe it's helpful for you.
But on European ships this three types is quite normal.