So, you'll know what light means. Anything you forget can be purchased in Europe. It may not be at bargain prices, but you'll be able to get it. Plan to rewear some of your clothing. No one cares that you have had the same shirt on two days in the same week.
Backpacks are good.
Pulling-suitcases are too. Read the packing list in your Orientation packet. I can tell you, you can't really go to the wrong place in Europe. Additionally, I like to bring a huge bottle of water and a good book for the flight. Believe it or not, there is always more paperwork to complete.