I mostly use yarn that has at least 50%, or more, of cotton or bamboo content. Most of my dresses will use 100% of bamboo or cotton. I will note which dresses use which yarn in the dress listing.
My more affordable dresses are available in acrylic yarn. I do this to keep the dress more affordable. You will get the luxury look, but at a great price.
There is a type of cotton yarn that is sturdier than other types of cotton yarn that I use to make dresses and tops that will hold the chest. I use Lily’s Sugar N Cream for this. If I can find another brand, then I’ll use that, but for now that’s the only yarn that I’ve found that holds well, but also comes in a large cone and not just small balls.
I do use mixed fibers for certain dresses. Those dresses don’t require to hold up your chest. I also like the color options for those yarns, and the yarn is still soft and hold its shape well.
Lion Brand Coboo Yarn

This yarn is made with 51% Cotton and 49% Rayon from Bamboo. This makes for a very soft yarn that is lightweight and flowy.
Hobby Lobby I Love This Cotton!

I Love This Cotton! yarn is made with 100% cotton. The cotton is silky soft. It is a bit of a heavier yarn, so each dress/skirt that is made with this yarn will be a little bit heavier than expected.
Caron Cotton Cakes

I love the Caron Cakes yarn. The yarn is easy to work with, and comes in many colors. I found out that this yarn is 60% cotton and 40% acrylic. It’s still very soft, and easy to work with. This yarn is exclusive at Michael’s.
Caron Painterly Cakes

This looks to be a more colorful of the Caron Cotton Cakes yarn. It is the same amount of cotton and acrylic. 60% cotton and 40% acrylic. I haven’t tried this yarn yet, but I will soon.