What is the best Yakuza game to recommend a begginer?
Yakuza 0 is a prequel, so you'll miss out on all the "hey it's that guy but young!" moments. Some series callbacks will go over your head, but it's a good time.
Yakuza Kiwami 1 is a remake of the original Yakuza 1. Kiwami 1 came out after 0, so it's taken on some lessons of the previous entries and their engine, so iit plays similarly to 0. Same goes for Kiwami 2, but games 3-5 are just re-releases that came out on PC two years ago. This means that both graphically and to some extent gameplay wise they might be a bit of a shift.
Yakuza 7 (Like A Dragon) is a soft sequel: it helps if you know what happened before or who that manic guy Naruto running down a building and throwing knives at dudes is, but it plays fine on its own. The gameplay is a radical shift though: from a brawler to one of those action-turn based RPGs that got popular lately.
The Judgment duology is a decent spinoff, but not where I'd start the series. Same for Like A Dragon Ishin, which has a historical setting where most of the cast is played by people you'll recognize.
TL;DR: Yakuza Kiwami 1 if you want to get the absolute most out of Yakuza 0, Yakuza 0 if you don't care about going "hey it's that guy but young!" or seeing how the games changed over time as they released, if you hate brawlers but like action-rpgs pick up Like A Dragon. Yakuza 0 was released after 5, so if you start with 1 play 0 before 6.
And if you enjoy Fist of the North Star, pick up Lost Paradise along the way if you've got a PS4 laying around.
In any case, there's bundles for 0-1-2 and 3-4-5 on sale on Steam. The first one is a no-brainer if you want to start with the series, but because the sale lasts only two more days you either will have to make up your mind quick if you don't want to spend before you know you want to. Then again, if you don't have a lot of time to play you can start with the first bundle and pick up the second in the next sale if you like the games.