Great tips! Very interesting to read about since I'm living in Europe (Belgium). Some things to add:

Low budget airlines:
Use sky scanner (app/website) to find the best deals, planned a round trip in Africa only using this app, was a major success

Another cheap way to get around on train is buy the European rail pass:
https://www.interrail.eu/
1 pass for 30 countries, and you can sleep on certain trains :)

Look for B&B's, they are run by local people who know some money saving tips & tricks.
We have some of the best B&B's in a very affordable price range. Find the best ones on Airbnb (app)

Hitchhiking pro tip as a former scout:
Wear a youth movement uniform and always have something to write on, so people can see clearly where you want to go.

Secret tip:
Make some European steemian friends :)

Save travels !