I think your grammar level is more important than your Wanikani level. I’d advise getting to JLPT N5 grammar level/end of the Genki 1 textbook before starting reading. For me I was Wanikani level 25 by that point but definitely could have started reading at a lower level if I’d got my grammar going earlier.
My first book was なぜ？どうして？せかいはふしぎ which I read along with the Absolute Beginner Book Club. That was a non fiction book about the world, aimed at 2nd grade Japanese students.
The Absolute Beginners Book Club has read lots of other books since. You can read any of those books and look at the vocab sheets and translation questions that were posted in the discussions of those books. There’s a new manga starting next week. The home thread for the book club is: