The thing nobody mentions about sequin tops is what happens to your skin and everything near it after the third or fourth wear. The cheap ones start shedding, properly shedding, little discs turning up in your bra, stuck to the inside of your coat, glittering away in the washing machine filter for weeks after you've stopped wearing the top at all. A good one keeps its sequins where they're supposed to be, stitched through rather than glued on, and you can tell the difference with one firm scrape of a thumbnail before you've even paid for it.
These aren't a top for sitting at a desk under fluorescent lighting, and they're not kind to anyone who needs to move a lot without catching on things, tights, scarves, other people's jumpers at a party, all of it wants to snag on cheap sequins. They're also not forgiving if you're after something that skims, because the backing fabric sits stiffer than you'd expect and shows every line underneath it. Before you buy, check the inside seams with your fingers, not your eyes, because that's where you feel whether the sequins are sewn on individually or in strips, and strips are the ones that come away in a long run the first time one catches. Check the weight of it too, held up rather than on the hanger, since a top that feels like nothing in the shop can feel like chainmail after two hours of a party once your arms have been up and down doing all the usual things arms do at a party. Darker shades wear better over a full evening, a deep green or a near black that catches light without demanding you match it to anything, whereas a very pale gold or silver shows every mark, every bit of fake tan transfer, every greasy fingerprint from someone's drink.
Worn properly and looked after, a decent sequin top earns a strange kind of loyalty, the sort where it comes out for three or four occasions a year and still looks the way it did the first time, rather than arriving home from the first wear missing a patch over one shoulder like a moth's had at it. Hand wash it, cold, inside out, and never wring it, because that's where the glue backed ones lose their nerve entirely and the stitched ones just go on being stitched. Let it dry flat, away from a radiator, and resist the urge to iron over the sequins directly unless you fancy watching plastic go cloudy in real time. Over a year or two the better ones soften slightly at the seams and the sequins dull just a touch, which honestly only makes them look less like fancy dress and more like something you actually own.
A good sequin top is one of the few things on the high street actually worth paying twice as much for.