Nausicaa manga

Whenever you feel comfortable with spending a lot of time on going through it. Your first read will always be a struggle, regardless of when you start it. The only recommendation I can give is that you at least familiarize yourself (or rather yourselves now) with the most common (so N5) grammar patterns. This means either reading through genki I for example or going through a bit of tae kim’s guide, or choosing a youtube series you aren’t completely bored to hell by. I personally started reading at about level 15-20 before my reset, if I remember correctly. If the manga has furigana, your vocab knowledge won’t be the issue (if it doesn’t, it might be way too painful so I recommend starting with something else like the Absolute beginner’s book club)