interrail friendly country - not so many seat reservation

Germany, Austria, Switzerland are basicly free of mandatory reservations (with very few exception that can easily be avoided)

Same for Slovenia and Croatia. 

Netherlands and Belgium are also fine to travel without reservations. (there are reservation free alternatives to the trains with mandatory reservations)

Easter Europe has more mandatory reservations, but those are usually quite cheap.(<3€)

Spain, france and italy have mandatory reservations on all highspeed trains and they are quite expensive. 

Thank you for your reply. Do you have advise how to get from Luxembourg to Portugal avoiding seat reservation. Honestly I am disappointed that seat reservation is must for so many connections. Interrail is not good option in this part of Europe. 

​@Kasia 

If you want to avoid reservations, it will take three times as long, and you will probably have to spend one more night on the way or use more travel days as with high-speed trains.That could be more expensive than reservations.

You can find information here:

https://www.seat61.com/Portugal.htm

It is a good idea to use the planner of www.bahn.com. In the extended search options, you can exclude High Speed Trains, finding you a route without TGV and AVE’s, trough France and Spain.

Best to split up your journey in smaller portions.

Although I don’t think there’s any entirely reservation free route to cross Spain. All the local trains to/from Badajoz and the majority from Vigo require reservations.

Austria…...OBB run an efficient, modern, safe railway in a beautiful scenic country. Low reservation fees & if 1st class, you are able to use the very pleasant lounges.