I’m working a crochet ribbing because I don’t know how to knit:
I went down a couple hook sizes (from 3.25 mm to 2.75 mm) and am doing rounds of post dc stitches, alternating front to back to create a ribbed look. It doesn’t have the same stretch to it that a knitted rib does, but my top is large enough that with the smaller hook size it fits me right.

First I worked a round of dc stitches around the bottom opening, then worked the post stitch rounds from there. With my hook size and desired finished size, the amount of stitches that seemed to work best was a dc in every dc, 2 dc in each corner join (1 in each motif), and (2 dc, 3 dc, 2 dc) in each group of chains at the middle of each motif.

I’m doing the main ribbing (front and neck) in turned rows instead of rounds, because it’s the simplest way to get it to match the way the knitted version is joined in the front. I’m using a slip stitch to join to the front center square after every row instead of stitching it up later. I’m placing decreases at the corners of the neckline as suggested in the pattern, and that seems to be working out well. I’m decreasing 2 stitches every other row in each corner.