Help with transportation in Europe

Hello guys,
So I’m gonna spend a month in Vienna in September and I can only travel on weekends and I have two weeks in October to travel around as well.
I am trying to choose the countries/cities I will go to and the best way to get there.
Here’s the list of countries/cities I want to go to (Feel free to suggest crossing out or adding any countries) and please tell me the best way to get to each country from Vienna.
My transportation budget is around 250-300 Euros maximum
1) Amsterdam
2) Croatia
3) Paris, Toulouse, Nice, Bordeaux
4) Munich, Hamburg
5) Zurich
6) Milan
7) Barcelona

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