I suggest starting with something with stretch. This likely means an animal-based fiber (wool is the natural choice).
Alpaca, while very soft, tends not to be a very stretchy fiber. It’s also a more expensive fiber so it’s not one that I recommend you try at the start.
They call it poor-man’s cashmere and it can quite supple. But, if you’re just starting out, try to stay strong and stay away from the alpaca. While it’s very soft, it’s also not very stretchy and tends to flatten out when knitting it. While you can work with those tendencies, I suggest you work with a more traditional fiber when starting out.
I suggest avoiding plant-based fibers in the beginning because they don’t have the stretch (in general). If you don’t want to use animal-based fibers, there are some plant-based blends with stretch as well. You’ll need to assess them yourself to determine if it has that give.
While elastic *will* make your yarn have more stretch, knitting with it can come with some challenges. It can be harder to get a consistent gauge, and when you’re starting out, achieving a consistent gauge can be challenging enough all on its own.
There are lots of other fibers as well, but we’ll keep it simple and just focus on these few.
Regardless of which you choose, you’ll have a lot more options with animal-based fibers. This is just the fact that there’s a lot more availability for those types of fibers.
There’s enough to say about “Superwash or Not” that we’ve dedicated an entire post to it. Look for that next week.