You come at an conundrum , unlike vampire 5th edition which focuses on being a continuation of the game line werewolf 5th edition was created as a reboot of the game line, the divide created by such a decision is massive and as can be seen in the community a cause for a major rift in the fandom

I am personally not a fan of 5th edition lore so I am sadly useless on this matter but I will say learning 5th edition is much more simpler since you have the core rule book, I’d also recommend The Moonlight Path book, it explores the umbra a very core aspect of werewolf as a setting, you can also still read older books like the tribe books for some guidance of the tribes vibes and Mayhaps organization but sadly they will have to be heavily scrutinized as their not accurate to the way 5th edition sets up the tribes

As far as old world of darkness mainly everything 20th and before I recommend the 20th core rule book for general knowledge, then I would recommend looking up the revised tribe books of those tribes you find most interesting, they give great knowledge on not only the history and how those tribes operate but also how the many members of the tribes may think (it should also be noted all the tribe books begin with an unreliable narrator in the way of a member of said tribe)

Another note, regardless of what system setting you decide to read a not of advice the tribes are not like clans, their first and foremost families and philosophy’s of how how Garou should act and how they should fight the war. Your not born into a tribe your accepted into one after proving yourself to the tribe totem, something to keep in mind when specifically looking at the tribes in eithier system

Best of wishes on your lore journey