The thing nobody tells you about ribbed dresses is that the rib shows everything underneath. Every seam of your underwear, every crease, the lot. Buy one without thinking about what goes on under it and you'll spend the whole day picking at the fabric wondering why your pants have a starring role. That said, once you sort the underlayer out, a good ribbed dress does something very few other dresses manage, it skims without clinging, and it moves with you rather than just hanging there looking neat and lifeless.
How it ages depends almost entirely on the weight of the knit, and this is where cheap and good properly part ways. A thin, bargain rib starts out looking fine on the hanger and within a few wears has gone baggy at the bum and seat, stretched out at the knees if it's long, and thin enough at the thighs that you can see through it under certain lights. A denser knit holds its shape through a season of actual wearing, washes well on a cool cycle, and comes back from the drier without the ribs flattening into a smooth, characterless surface. I always check the weight in the shop by pinching the fabric between two fingers, if it feels thin enough to see daylight through when held up, it will not survive much. I also check the shoulder seams and the hem, because a cheap rib often puckers along both once it's been through a wash, and the stitching at the neckline tends to go first on the weaker ones. Worth running a hand down the inside too, some ribs pill almost immediately against tights or coat linings, and that's a fight you don't want to have every time you get dressed.
It clashes with anything else that's clingy or textured in the same way, so a chunky cable knit cardigan over the top just adds bulk in all the wrong places, and tights with a visible seam or pattern tend to fight with the vertical lines of the rib rather than sitting quietly underneath. Structured blazers work better than soft, draped ones, because the dress already has plenty of its own shape and doesn't need more softness layered on top.
The mistake to avoid is buying your usual size out of habit. Rib stretches with wear in a way that woven fabric doesn't, so a size that feels snug and slightly too tight in the shop is usually right, and a size that feels comfortable on day one will be loose by the end of the week.