I'm studying Dutch in Leiden now
and for one of my courses we're expected to learn 15 words a day from Thematische woordenschat voor anderstaligen. The book is a sort of thematic dictionary with definitions of words in relatively simple Dutch. It contains 6000 words, 3000 basic words with 1000 of said words being elementary and 3000 more advanced words. It also includes idiomatic phrases that use said words. And some pictures! Leiden is likely the best university in the Netherlands when it comes to languages and they consider their Dutch program to be fairly intensive. In other words, 15 is their answer to this question (including weekends and holidays
) and from my experience, I'd agree. Any more is really a bit too much IMO if we're talking about explicitly studied vocabulary.
Personally, I'm super happy about their choice of book. I've always wanted to just pick up a dictionary and start learning words, but I know that's a bad idea. But with this I can do just that. I think that when it comes to word lists, you don't need them but I've found them super helpful in the beginning. I learned a few hundred words from a 1000 words list when I had just started Dutch years ago and I plan on learning every one of these 6000 words like the back of my hand, even if it wasn't required. 6000 is also the sweetspot for a language like Dutch I feel. More and you'd be getting into vocab that'd vary with each individual but if someone wants to learn a language fully (and not just for one specific purpose) then I think a specially prepared source for the first 6000 or so words (not a frequency list! There's lots of problems with those) is safe to memorize.
As for how to memorize them, well, the course focuses on vocabulary and writing. We learn words and then write things with them. And that's also the method that I've found works best for me. Speaking helps too of course (and there's courses for that too) but writing is all I personally need to learn the vocab.
Why do all my posts about materials sound like ads? Ugh. Haha. Though I do sometimes talk about resources I don't like so hopefully that makes up for it.
But yeah. I think that you don't need word lists and that you could learn everything through reading, but I find them helpful if done properly and then I have something that I know someone somewhere thinks I should learn. And that makes me feel like even if I'm not on the best path, at least I'm on some path!
All comments and corrections welcome.