Hello cyprusbabe, welcome to Cruise-Chat! The Radiance is a beautiful ship and the food is the best of any of the RCCL ships I've been on.
There are two formal nights. I think most people ware their best on only one which would be the second night of the cruise. Jeans will be fine during the day in either the Windjammer or the main dining room. Other than formal nights, you could even ware jeans in the main dining room if you want. Formal nights are when people are getting their pictures taken looking there best. Now that you have to pay for the 1st and 2nd piece of luggage, you make want to try to pack light. I only ware one tux, and my wife packs one Formal dress. She has a couple of pants suits that seems formal to me. I think think my wife would look great even in a gunny sack.