I’d say that the best option is what you have on hand, or whatever is easier to get. Nothing beats just getting started and learning as you go. Still, if you want something that is easier to work with, I can think of a few good options.

Worsted-weight yarn is a good option. It’s a medium thickness that is easy to handle, not too thin, and not too thick. It’s versatile and widely available, making it a great option for beginner projects. I remember using it made learning new stitches less frustrating because I could see my work clearly.

Another great choice is acrylic yarn. It’s affordable, comes in many colors, and is very forgiving. If you make a mistake, it’s easy to unravel and start over.

Once you’re ready to move on to more intermediary projects, I recommend getting a knitting kit. Something like the Fair Isle knitting kits on this website is a great option because the kit comes with all the materials you need and instructions on how to complete the project.