I do not have any fancy notebooks, but notebooks are a central tool for my language learning. My preferred notebook is Moleskine's extra large cahier. Some things I like about it:
-It is moderately priced, around $5 USD each.
-It has a soft cover, and the pages stay open. Notebooks with hardback covers tend to close shut.
-It is large enough to use productively. Small notebooks are easier to carry around, but are difficult to write in.
-It does not have a metal spiral that obstructs the hand.
Here, I use the notebook to keep track of Korean words, but I usually write down sentences rather than individual words. I also work in reviews of words and phrases I've forgotten into the notebook.
https://imgur.com/a/B7MSEoV