At what level you can start to read very simple text?

^ I came here to say that!

And to link these:

^ Very detailed guide on tools and resources to start reading Japanese.

^ This one will be veeeeeery useful as well!

P.S.: My personal experience of learning to read is a total mess, nevertheless, I don’t recommend children’s books (tried that, went like this: :thinking::scream::sob:) for reasons mentioned by @2tea and depending on your motivation, dedication and available time would second the recommendations of Satori Reader, Yomitan and free Tadoku books at your current Wanikani level, @Monops79 !