Twenty-one of our kits specify cotton. None contains wool in the proper sense.
This isn't a matter of taste. Wool is stretchy and fuzzy: it pulls the stitches open, blurs the outline, and lets the stuffing show through. Cotton is dry and firm, and it holds an edge.
The right weight
Medium cotton — what listings call DK, or a 3 to 4 needle yarn. It's what almost every shop-bought kit contains, and what patterns assume.
Finer, and the piece takes twice as long. Thicker, and it loses the detail in the muzzle and the paws.
DK / medium cotton
the amigurumi kit standard
Chenille, plush yarn
very fast, but no detail
Acrylic
works, less crisp than cotton
Real wool
avoid for a first piece
How much yarn one takes
Far less than a garment. Our kits state two to three 25 g balls, or 56 metres of yarn for a complete rattle.
That's why an amigurumi stays a cheap project even when you buy the yarn separately: we're talking tens of metres, not hundreds of grams.
The cheap-bundle trap
Multicoloured mini-ball bundles are tempting and often well reviewed. Check the weight first: many are fine yarn, on which a pattern written for DK gives a piece half the size of the photo.
An amigurumi that comes out half-size isn't a skill problem, it's a yarn problem.
