Silk dresses used to mean one of two things: something inherited and slightly too precious to wear, or something cheap with "silky" in the name that creased if you looked at it. The real stuff has got easier to find at normal prices in the last few years, and easier to wear too, with slips cut less fussily and finishes that don't scream delicate. It's better than it was, though the gap between a good one and a bad one is still enormous.
Before you buy, check the weight of the fabric against the light, because a true silk with any body to it won't be see through at the thigh in a way that forces you into a slip underneath. Look at how the seams are finished on the inside, a raw or fraying edge there tells you how it'll behave after a few washes. Check the care label properly rather than assuming, because a lot of "silk" dresses now are a mix, and that changes everything about how you treat them. And look at the closures, a zip that's been set in badly will pull and pucker at the side seam within weeks, however nice the dress looks still on the rail.
For colour, anything with too much white in it shows every mark and every deodorant line, so I'd steer towards deeper tones, a true black, a bottle green, a berry, something that hides a day's wear rather than announcing it. Prints are forgiving in the same way, a small repeat pattern disguises more than you'd expect. If you're buying your first one, go for a simple slip or bias cut in a dark solid colour rather than anything with a lot of detail, because that's the version that still looks right in three years when the cut of the moment has moved on.
It pairs with almost everything already hanging up, which is the nice surprise of owning one. A denim jacket over the top takes it out of event territory completely, flat boots make it walkable, and a plain cardigan does the job for anything that isn't quite warm enough weather. It layers under a coat for winter better than people expect, mostly because the fabric is thin enough not to bulk up under anything.
Where it falls short is resilience. However well made, silk shows a hot wash, a hot iron, or a day in a crushed bag, and no amount of good buying undoes carelessness once the damage is done.