You can take an umbrella or a light raincoat. Personally, I prefer a light raincoat, which is more convenient and practical.
It is best to bring personal toiletries, because small and medium-sized hotels in Europe do not provide toiletries, and only four-star hotels have these things.
The power plugs in Europe are round holes, which are different from those in China. And the hotel has no adapter, so buy one.
What is your language like? If you can't bring a fast translator or a simple mobile phone with translation function, you can communicate simply if necessary.
A camera is essential!
Prepare some medicines and first-aid medical supplies according to your physical health, in case of emergency, just a little, not a few years!
Since it is a tour, it is most comfortable to wear jeans and sneakers. Oh, you have to prepare a formal suit, because there are many high-end coffee shops and restaurants in Europe, and you are not allowed to enter casinos without formal clothes.
You'd better pack your passport and money separately. If you lose your passport abroad, you will be in big trouble.
Tap water in European countries can meet drinking standards, so hotels do not provide boiled water, nor do they provide boiling water utensils, and they have no habit of drinking boiled water.