Make sure to complete Sacred Hunt early on

There are, of course, those absolute maniacs who will do 80 hours of sidequests before going through the main campaign, and bless your hearts for your ambition. But if you’re using a Spiritborn character, and you’re at least at level 20, if you do literally nothing else in the campaign, make sure to hit the Sacred Hunt quest—it unlocks the Spirit Hall.
Hopefully by then, you have a good idea which abilities suit your personal style, so you can definitively pick which animal to specialize in, but there’s also a fringe benefit to keep in mind: Selecting a spirit also adds that animal class to every single skill you currently have. That creates some interesting synergies off the bat, allowing any attack to build Ferocity for Jaguar attacks or Resolve for Gorilla. It’s actually a good excuse, before you get too deep in the weeds on your skill tree, to go back, prune anything you aren’t using, and fine-tune things to get those passive abilities generating with every ability.