I would recommend to play all of the mainline story (Yakuza 3, 4, 5, 6, 7 and 8). The story is a little stupid at times but overall it is good. And if you do all of them in chronological order it is much more impactful when you know the background of characters and their relationship with others.

I have to say that i played a lot more of the Judgement games. I haven’t played the Ishin games and Dead Souls, i’m not that much interested to play them.

In my opinion, you shouldn’t think like that. If you love the franchise, take you time and just have fun playing what you want.