What level would I be able to start reading Yotsuba?

I agree 100% with Leebo. Wanikani will help you, but it’s not a “cure-all” solution.

Just want to add that the forums have a book club for yotsubato. It’s a place where you can check people asking questions and more advanced learners helping with cool explanations. It will certainly make your reading flow much better :smiling_face: