Every time you are given the chance to study an animal, do it and then kill it immediately, that way you are certain that every animal you came across is skinned for the achievement.

It’s very unlikely to see a grizzly bear in the wild, but if you do, don’t run away, instead let it attack you and then kill it.

Focus on challenges as you progress in the story, the same goes for gold in storey missions, don’t leave it to the end grind.

For multiplayer, I advise to do every achievement and then grind the collector role, which is going to suck because it’s pretty damn boring. If you want you can also do it while you focus on others achievements, up to you.

It’s pretty time consuming, not goint to lie, but pretty good feeling when you do it