Ninjas all give initiative by having them unlocked. It comes from their star level. If you get a lucky unlock from a draw, you'll get more than the base ninjas. For example, Kisame, Sasori, or Hidan from the Seal Treasure give about 12 init each by unlocking them at 3 star. Leveling up stars gives you at least a few init for the beginning ninja. So yes, it's quite easy to have 80-100 init at that level.