I just started making a couple of wearable too. I am making them for an 11yr old so wanted to ensure proper coverage and washabilty.
The first one I used a double strand of mercerized cotton light worsted weight (4 weight) it definitely had proper coverage, but is extremely heavy. I have abandoned that one for now because it was supposed to be for summer. I switched to a DK 3 weight in acrylic, using a single strand, same stitch, and a 4.0mm hook for the top portion provided the proper coverage and is considerably lighter, appropriate for a summer dress (not completed yet, but here is a picture). I switched to more open stitches and a 5.0mm hook for the bottom portion because she will wear shorts underneath it.
The cotton doesn’t stretch as much and is supposed to maintain shape better. Acrylic is stretchy, light, and can be very soft. I just received a gift of some bamboo rayon yarn that I can’t wait to try.