I'm kinda of a down to earth girl... don't really own anything fancy.... I found a nice silky pant suit and silky blouse... will I be OK on formal night?
Dress standards vary pretty radically between cruise lines. That outfit probably okay for a "formal" evening on Carnival or Princess, but it sounds like something that would be much more acceptable for an "informal" evening than for a "formal" evening on Celebrity, for example. Another option would be to wear a dress that you wore to a prom or as a bridesmaid, if you have one.
If you prefer casual dress in the eveing, you might find that Oceana Cruises ("country club casual" every evening), Norwegian Cruise Line ("formal optional" or "casual" every evening), or even Windjammer Barefoot Cruises (shorts and "T" shirts even in the evening) would be your best match.