The yarn used is Schachenmayr Catania, but good alternatives are Durable Coral or Katia Capri. These are all 100% cotton, which is an ideal yarn for amigurumis.
You’ll need one skein of the main color and only some leftovers of the other colors.

The used hook size is 2mm (UK 14, US B/1).
When you use this yarn and hook, the finished size of the dragon will be about 12 cm.

If you use other materials, make sure you use one hook size smaller than recommended on the wrapper, so your dragon will be nice and tight.

I recommend the pattern to be used as an intermediate skill level pattern.