Not every type of yarn is suitable for Amigurumi. The type of yarn you choose for crocheting toys can either make or break your project.
It is possible to pick any yarn you want for your amigurumi or you to use the yarn that the pattern recommends you to use.
I prefer to use acrylic or semi cotton yarns for my amigurumi because they keep the shape of the toy nicely and toys can be machine washed. Most of these yarns comes in sport or DK weight (fine to light/medium) yarn.

Of course you will need a crochet hook) The size that you will need will depend on the yarn that you’ve picked. The label of your yarn contains information about what hook sizes are appropriate to use.
For Amigurumi, it’s recommended to go down a couple hook sizes to attain a tighter gauge so that there are no holes (preventing stuffing from coming out) with very small, tight stitches. Thus, even though your yarn label might say to use a 5.5 mm crochet hook for that particular yarn, it’s better to use a smaller hook(3 or 3.5 mm hook would be fine).

Stuffing is a very important part of your work, and it will determine what your finished toy will look like.
I always use Polyester Fiberfill Stuffing (Poly-Fil). It’s a super popular stuffing! It is inexpensive and easy to find at almost any craft store! This stuffing is soft and flexible, it lends itself well, so it can stuff the most sophisticated shapes. It is machine washable and resists moisture, dust and germs making it non-allergenic.

Stitch markers are cute clips that can be used to mark where you start and end your pattern. Particularly useful if you are working on a round pattern. Like a stitch marker you can use a scrap piece of yarn. Use a contrasting piece of yarn, preferably something slippery and a lighter weight than your current yarn. This way you will be able to pull it out easily later, and it won’t leave gaps or affect your gauge. When you complete your first round, lay your marker yarn over your work before starting the next round. When you work the first stitch of the next round, the yarn will be trapped between the stitches. Here you can watch a video on how to use a scrap piece of yarn as a stitch marker(click on the link):
https://youtu.be/Vs--AuI9l-c

With amigurumi, you often crochet all body parts separately and then sew all the pieces together at the end. You can use a regular sewing needle, but I think that a yarn needle, which is also sometimes called a tapestry needle is an essential part of your basic crochet materials. It looks like a sewing needle only the eye of a yarn needle is quite large, so it can accommodate even the heaviest yarn. Also unlike a regular sewing needle, the tip of a yarn needle is blunt. This is because a sharp tip would end up splitting or fraying the yarn. Many yarn needles have tips that are curved, but a straight tip also does the job.

Safety eyes are specifically made for knitted, crocheted or fabric toys, usually made of plastic and come in a variety of sizes, shapes, colors and styles. They are easy to attach but difficult to remove. Safety eyes are attached before you stuff and close your amigurumi, and have a little washer that holds the eyes in place. If you don’t want to use safety eyes, simply embroider them on instead.
Here you can watch a video on how to use safety eyes(click on the link): https://youtu.be/FXgFHEa_TYo