There's a particular kind of week, the one where every meeting runs long and you haven't washed your hair since Tuesday, where earrings do more work than anything else you put on. You can repeat the same jumper three days running and nobody notices, but swap plain studs for something with a bit of movement and suddenly you look like a person who has her life together. I don't, for the record. The earrings are doing a lot of lying.
Before you buy, look at the bits nobody photographs well: the back of the stud, the clasp on a hoop, the join where a drop earring meets its hook. Cheap metal tends to show itself first at the earlobe, a dull patch or a greenish tinge after a few wears, which is a nickel problem more than a fashion one. Check whether the fastening is a simple push back or something more secure, because a flimsy butterfly clasp will lose you an earring on a train platform at some point, usually the better one of the pair. Hold them up to the light too. A good finish doesn't look painted on.
For everyday wear, small gold or silver studs sit under almost anything without a fight, a crew neck, a collared shirt, hair up or down. Hoops are the ones that change a plain outfit the most, a white tee and jeans looks considered the second you put a decent sized hoop in. Statement or drop earrings want a simpler neckline doing nothing else, otherwise your face ends up competing with your own jewellery, which is a strange thing to lose.
The difference between a good pair and a disappointing one is mostly in what you can't see until you've worn them a while. Solid metal has weight to it and keeps its colour, plated pieces thin out at the edges and flake where they rub against skin. Good hoops are soldered properly at the join, not just pinched shut, so they don't catch on scarves or distort into an oval after a month in a coat pocket. Sterling silver tarnishes a bit, that's just what it does, but it polishes back up, whereas cheap alloy dulls and stays dull.
If you're starting with nothing, go for a plain pair in gold or silver first, something small enough to wear with everything and sturdy enough to survive being lost down the side of a bag and found again.
That same jumper you've worn three days this week looks like a different outfit with the right pair in.