I used to do 10k, as well as iKnow, before in the past; and WaniKani level that made reading easier without Furigana was around 30-40, I think.
Still, I relatively recently complain that there are too many vocabularies in Japanese. - Well, only some are of immediate importance…
I would rather say that best vocabulary sources for your reading would be
- Your textbooks, as well as grammar sources, like Tae Kim.
- Collecting vocabularies along the way, and properly looking up. Vocabularies that I learnt in the past few months come back a lot.
About immersion (Pokemon game), it is hard to pinpoint where to start, and how many understanding / grammar to know, before starting; but it is also eventually important that you would want to understand well.
- To balance the risk of poor understanding and never improving, I study some other native materials concurrently.
- Listening is also important to reading correctly without Furigana, even if listening is half-assed, like for myself. Some topics textbooks well help, like 八個, while some others will just miss. (afaik, native Furigana texts don’t Furigana numbers; also if there is an alternative Furigana or emphasis dots, the original reading is dropped.)
My current way of Anki (+ WaniKani API) is here. Nonetheless, I only really do Definition => JP.
Create my own mnemonic, or repeatedly create a new one if it doesn’t work. About the Kanji, making a mnemonic based on wrong Kanji (or wrong vocabulary components), false etymology or not, works too.
A lot of example sentences and context may help; but not always, nor immediately help.