Out of all the supplies you use to make amigurumi, polyfil is one of the super important ones that we care least about. It goes on the inside of the amigurumi and gives your work shape and body.
I strongly prefer generic polyfil - the kind of polyfil that feels more like cotton gives my sensory issues the heebie jeebies. So I prefer the stuff that feels like acrylic clouds. Also, I told my daughter they’re called “Clouds” and she will often ask to play with my “clouds”.
There are more options and tricks for stuffing your amigurumi. You know all those yarn tails you get after weaving in your ends? If you save them, you can use them to stuff your next amigurumi!
Also, when you make an all black amigurumi - like a black unicorn, and you’d like to stuff it, it can be a little odd looking to stuff it with white polyfil as the white will peek through all of the holes of the crochet work. If you don’t like the look of the white peeking through, there are ways around it! You can take a nylon stocking, and fill THAT with polyfil as you stuff it inside the amigurumi. The nylon stocking will contain and mask the bright white and you won’t notice inside your work. Your second option would be to pick up some very cheap black yarn and use that to stuff your work. You can find cheap black (or any color) yarn at thrift stores and in the clearance section of your local big box craft stores. Stuffing amigurumi with yarn means that your amigurumi will be much heavier than if you stuffed it with polyfil, but you will not see the inner stuffing through your crochet work AT ALL.
I hope this helped!!