Gauge doesn’t matter, you can use thicker yarn to make a bigger Amigurumi. You can crochet or knit some clothes for your cat as well. I made these cats for babies, so I embroidered eyes & snout on the head using scrap yarns. You are welcome to replace it with safety eyes & safety snout.
You will need to know how to knit an i-cord, if you don’t know how to knit an i-cord, go to YouTube search for tutorial, there are plenty video teaching people how to knit an i-cord.