My first dressing gown was a thin polyester wrap thing that came with a matching eye mask I never used, and within a month the belt loops had torn clean off from being yanked too hard every morning. What it taught me was that a robe lives or dies by its fastenings and its weight, not by how nice it looks folded up on a bed.
A cheap one tends to be made from a fabric that feels fine in the shop and then goes thin and see through after a few washes, with a belt that's really just a sewn on strip of the same stuff, no proper loops, nothing to stop it sliding open at the worst moment. A good one has a bit of actual weight to it, whether that's a thick waffle cotton, a brushed fleece, or a proper heavy satin, and the difference shows up in how it sits on your shoulders rather than just hanging there. Look at the belt loops, which should be set into a seam, not stuck on as an afterthought, and check the pockets are deep enough to hold a phone without gaping. Decent stitching along the seams and hems matters more here than almost any other garment you own, because a robe gets put on and ripped off more times in a week than most of your actual clothes.
Season and occasion wise, a robe does different jobs depending on the fabric. A lightweight cotton one earns its place in summer, after a shower, pottering about before you've decided what you're wearing. A thicker waffle or fleece version becomes the thing you reach for from October onwards, worn over pyjamas with a cup of tea, or thrown on for the ten minutes between getting up and getting dressed when the heating hasn't kicked in yet. Satin sits somewhere else entirely, more for evenings, getting ready for something, than for actual daily wear, and it shows the dirt and creases faster than the others, so it's not the one you want doing the heavy lifting every single morning.
On colour, I've learned to avoid anything too pale if it's going anywhere near a kitchen or a face mask, because a robe picks up tea stains and toothpaste marks faster than you'd think. Soft neutrals, a proper oatmeal, a dark forest green, a navy, all hide the daily wear far better than white or baby pink ever will, and they don't date the way a seasonal print does. Before I buy one now, I always ask myself the same thing in the shop: if I washed this forty times, would it still hold its shape, or would I be back here in March buying another?