The first thing I do with a yellow skirt is hold it up to a window, not a shop light. Yellow changes completely depending on what's lighting it, and a shade that looks warm and flattering under those little round ceiling spots can turn sickly the second you step outside. I've bought two skirts I loved in a changing room and barely wore again because daylight told a different story. So daylight first, always, before anything about fit or fabric gets a look in.
If you've got no yellow in your skirts at all, start with something in a heavier cotton or a cotton linen mix, cut as a midi rather than anything short or floaty. A bit of weight in the cloth stops it clinging or showing every seam of your underwear, which thin yellow fabric is especially bad for. Avoid anything with a slippery lining to start with, save that for later once you know the shade suits you. A straight or slightly A line shape in a mid weight cloth is the easiest entry point, it sits well without needing much thought.
On colour, mustard and ochre are the ones that sit easily against most skin tones and most of what's already in your wardrobe, they read almost like a neutral once you've worn them a few times. A soft buttery yellow is the next easiest. Pure lemon and anything leaning neon are lovely on the right day but they're unforgiving, they show tan lines, flush, and every crease in the fabric, so I'd leave those until you're confident rather than starting there.
How it ages depends entirely on the fabric rather than the colour itself. Cotton and linen soften with washing and get better with a few creases built in, that's part of their charm. Cheaper polyester yellows tend to go slightly grey or dull at the hem before anywhere else, so check that spot after a few wears. Wash yellow skirts inside out on a cool cycle, away from anything dark, and skip the tumble dryer if you can, heat is what makes yellow fade fastest and unevenly. Hang to dry out of direct sun.
This suits anyone who wants a bit of colour without going loud, and isn't afraid of being noticed walking into a room.