Quick answer: The best yarn is the one that produces the fabric, care requirements, visibility, and finished size your project needs.
Compare Yarn Fibers
Cotton gives clear stitches and limited stretch. Wool offers resilience and warmth. Acrylic is widely available and easy to care for, though texture varies. Blends combine properties; check the exact label rather than assuming all yarns with the same fiber behave alike.
Understand Yarn Weight
Yarn weight describes thickness, not the physical weight of the ball. Common categories run from lace and fingering through sport, DK, worsted, bulky, and super bulky. Compare metres per gram when substituting within a category.
Yarn for Amigurumi
Choose yarn with visible stitch definition, enough durability for handling, and a fabric surface that supports the intended details. Smooth cotton and acrylic are common starting points, but the pattern gauge and desired finish decide suitability.
Yarn for Learning Crochet
A smooth, light-colored, medium-weight yarn makes loops easier to see. Avoid highly textured or very dark yarn for the first practice swatch because it can hide insertion points.
Substitute Yarn Carefully
Match fiber behavior, thickness, gauge, and total length. Make a swatch, measure it, and compare the fabric before buying the full amount. A matching weight label does not guarantee matching gauge or drape.
Plan for Care and Use
Check washing instructions, colorfastness, abrasion, allergies, and who will use the finished object. Keep the yarn label and record dye lots when consistent color matters.
Sources
Yarn-weight categories in this guide follow the Craft Yarn Council Standard Yarn Weight System. A matching category label does not guarantee matching gauge. Safety notes for toys with small parts point to CPSC toy-safety guidance; Dezly is not a certification body.
Use the instructions and terminology stated by the pattern you are following. Make a swatch when gauge or finished size matters.