Start with 0 and go in chronological order.
0 -> Kiwami -> Kiwami 2 -> 3 -> 4 -> 5 -> 6 -> Yakuza: Like a Dragon -> Gaiden -> Infinite Wealth
The old games are very jank. I would only play them after you've played a bunch in the series if you're just curious about the roots.
https://imgur.com/u2HR4nG