Do you have any games, movies, music, shows, etc. in Japanese that you can listen to? I find that I pick up a lot of words through listening (even if I don’t know what they mean right away) before I encounter them on WaniKani. A lot of times I’ll make the connection between a vocab word and something I’ve heard before, and the vocab sticks a lot better because I’ve been exposed to it before.
Additionally, WK tries to provide mnemonics for readings you haven’t encountered before. Definitely make use of these mnemonics and try to picture them, even if they don’t stick the first time.
Lastly, do you use KaniWani or KameSame? These reverse-recall sites can really help stick the landing on unfamiliar vocab because you’ll need to approach them from a different angle and essentially get a second batch of tests.