Never played yakuza but bought 0,1,2 and 6. Heard great thing's about them.
The best advice I can give is read the Descriptions of the accessories. I can’t remember if it was 0 or 6, but I picked up a book that seemed beneficial only to realize 6 chapters later that it was making the game more difficult and caused more battles to happen. The description of the book was vague too. It was something like a highly desired book or something similar.
Because this happened when I was still new to the series, I got pretty frustrated and didn’t realize what I was doing.
I’d also recommend playing 1 & 2 first because even though they are remastered, the mechanics can feel dated compared to 0 & 6.
Finally, I believe Judgment is on sale too right now, you may want to pick it up (or at least keep it on your radar) if you have the extra cash/credit. It’s the first spinoff that takes place in the Yakuza world and you play a private detective and solve crimes. Imagine Yakuza meets LA Noire and Ace Attorney. At times Judgment can feel a bit long, but in the end I liked it a lot.