Safety eyes: 8 mm -> i recommend to get them in a set with different sizes
Hook: 2.5 mm -> my go to and absolute favourite crochet hooks are these Japanese Tulip Etimo Rose crochet hooks. I use them all the time!
Embroidery needle, tapestry needle -> i recommend get them in several sizes, with a blunt tip (so you don't split the yarn). You will need them very often in amigurumi: the bigger ones for sewing your pieces together and the smaller ones are perfect for embroidery or sewing smaller pieces.
Scissors or cutter -> if you prefer scissors i can really recommend these beautiful high-quality, vintage scissors
OR: If you prefer a cutter - like me - i really recommend this quick to grab yarn cutter
Stuffing -> i use this poly-fil stuffing, i recommend getting a larger amount, because in my experience it's used up fairly quickly