My first emerald dress came from a discount rail years ago, a polyester wrap thing that looked like bottled sea glass under shop lighting and like a traffic cone under anything else. It taught me that emerald is not a forgiving colour to buy cheap, because cheap fabric either goes flat and greyish or goes neon, and there's no middle ground where the green actually looks like the green you wanted.
If you've never owned an emerald dress, start with something in a matt fabric rather than anything with sheen. Satin and shiny jersey tend to throw the colour around under different lights, so it looks jewel toned in one room and a bit synthetic pond water in another. A crepe or a brushed cotton holds the colour steady, and steady is what you want when you're still working out whether emerald suits you at all. Go for a plain shape too, nothing fussy, because the colour is doing enough work on its own.
Once you've got one, it pairs with far less than you'd expect from how loud it looks on the hanger. Neutral tights, a plain black coat, a tan or black bag, all of it calms the dress down rather than fighting it. Gold jewellery works better than silver, I've no real explanation for that beyond having tried both for a decade and silver always looking slightly apologetic next to this particular green. A denim jacket over it for daytime turns it into something you'd wear to pick up a prescription rather than something that only comes out once a year for a wedding.
Good emerald fabric earns its keep over a full season if you treat it properly, which mostly means cold washes and keeping it away from direct sun on the line, because this colour fades unevenly rather than gently, patchy at the shoulders first. A dress that's been through a dozen washes should still look like itself, not like a paler cousin of itself. Mine has lived in the bottom of a gym bag more times than I'd admit and come out creased but not dulled, which is the real test, not how it looks fresh out of a bag at home. If it starts going a bit khaki after a few months, that was never proper emerald to begin with, just green with ambitions.
It suits anyone who wants one strong colour to do all the talking and nothing else to compete with it.