Asking for an Itinerary

Thanks a lot for your help ^^

If you want to go from Amsterdam to Spain without passing France, you need to find a ferry from UK, Ireland, manybe Italy or to Spain. I'm not sure if there is such a ferry. 

“Could someone help me craft an efficient and interesting itinerary please?”

Given your constraints it’s going to be tricky.  Very tricky.  You will get plenty of advice here, but taking account of these facts I think you will find that efficient is not going to feature in any itinerary -

1. you are starting in Amsterdam (sort of, you are actually starting in Paris, which is in France)
2. you don’t want to cross France (because you don’t want to pay excessive reservation fees, don’t like French people, or some other reason)
3. France is pretty big and wide and lies directly in the path between Amsterdam and Spain

Efficient - Amsterdam-Paris-Barcelona

Interesting - Amsterdam-Hook of Holland-Harwich-London-Plymouth-Santander.  This itinerary, while interesting, doesn’t actually involve a whole lot of trains.