What else should I do to learn Japanese effectively?

Hello, nice to have you with us :slight_smile:
There is a lot of stuff you can do outside Wanikani and it will not only depend on your current level of knowledge, but also how much time/money you want to invest. E.g. do you want to study completely on your own or go to a class or even get a private tutor?
Here is a link to a different forum that suggests a lot of other material besides Wanikani for reading/listening/writing/speaking.

Think about what your weak points are and where you would like to improve :slight_smile: And find something you enjoy, e.g. you mentioned reading books. There will be lots of material suggested. Just try out different things and enjoy it :blush: