A pearl necklace is the thing I reach for when an outfit is finished but feels a bit flat, a plain jumper or a shirt with the top button undone, and I want one small bit of shine near the face without looking like I tried too hard on a Tuesday.
Keep it away from anything already busy at the neckline, a printed blouse, a high ruffled collar, a chunky scarf, because pearls want a clear run to sit on skin or plain fabric, and they get lost or look fussy the moment they have to compete. The same goes for other jewellery in the same zone, a second chain or a statement collar necklace worn alongside pearls usually just reads as cluttered rather than layered, unless the lengths are genuinely different and you're deliberate about it. The honest limit is that pearls aren't a fix for a tired outfit, they're a finishing touch, and worn with something properly casual, like a hoodie or sportswear, they tend to look like they wandered in from a different day entirely. They also don't love humidity or sweat much, so if you're the sort who walks fast and gets warm, that's worth knowing before you plan a long day in them. Before you buy, check the clasp, a lot of cheaper pearl necklaces have a small fiddly clasp that's a nightmare one handed, and check whether the pearls are strung with knots between each one, which stops the whole thing scattering across a floor if the thread ever goes. Look at how they catch the light in the shop too, not just under the display spotlight, step towards a window if you can, because some finishes look warm and lovely close up and slightly plasticky in daylight.
For colour, go for an off white or a soft cream rather than a stark bright white, it sits better against most skin tones and doesn't look like it's trying to be a wedding accessory. A grey or a pale pink tinted pearl is easy to live with too, and tends to go further with navy, black, camel and most of the greys and browns most of us actually own. Bright white pearls can look slightly costume-y against anything other than crisp white, which is a narrower job than it sounds.
Tomorrow morning I'd wear mine with a plain grey jumper, dark jeans, and nothing else at the neckline at all.