Let's say you have 10 spirit. A pig needs 5 spirit to be tamed temporarily. If you tame it, you're left with 5/10, the other pigs will stay passive because you have enough spirit to tame them. If you have 9 spirit and tame a pig, you're left with 4/9 spirit, and all other pigs become hostile because you don't have enough left to tame them. Later, you'll be able to permanently tame animals at your base to have them follow you without needing spirit, but you'll have to feed them. At the start, you want only spirit, you never want to use your levelup for damage, that's the 1 useless levelup stat. You can buy a stat reset with silver coins to respec later if you did something wrong. I don’t remember if it was in town at an npc or in the store.
If you tame animals, your spirit will be consumed base on the required amount ex. Wild pig=5 spirit, and if the remaining spirit is not enough to tame the animal, it will aggro when it sees you
Every animal costs a set amount of Spirit. The level does not matter. FOr example Coyote=1, Wild Pig=5, Wild Cat=10. I'd suggest you to invest everything on Spirit because every other skill isn't very gamechanging.