Honestly, my best advice (considering reading begins in a few weeks) is to spend 10 to 20 minutes a day watching episodes of Cure Dolly’s Japanese from Scratch course. (Turn on subtitles.)
It’s okay if you don’t understand the material at first. You’re not necessarily expected to right away. Simply getting exposure to concepts will make a big difference in understanding them later. If you make it through the first 24 videos (start today!), you’ll be in a much better position to learn as you go if you stick with the book club.