Yarn suggestion for gauge?

I want to knit a shirt/dress for my daughter’s upcoming birthday, I’m confused by the “DK” yarn though. The gauge for the project is 24 sts = 4"; 34 rows = 4" in St st with a 3.75 mm needle and Berroco comfort Dk Yarn. I have tried making a gauge swatch with different needles and yarns, but can’t get the gauge. Is there any alternative yarns anyone can suggest which I might be able to use? I dont have the link for it, it’s on Ravelry as “Bilby” for anyone that can find it and knows how to link it. As always, any and all help is appreciated and thanks in advance!

http://yarnsub.com/yarns/berroco/comfort_dk_solids lists a whole bunch of possible alternatives, including easy-to-get items like cascade cherub dk, and various baby bee yarns (available at hobby lobby).

is your gauge too big, too small… is it an issue of stitches, or rows? oftentimes the stitch gauge matters more than the row gauge. i’m a tight knitter and often have to go up a few sizes to get stitch gauge.