The white co-ord comes out when you want to look like you've made an effort without actually trying, the kind of thing you throw on for a christening, a long lunch, or a work do where jeans would be a mistake but a dress feels like too much. I reach for mine on the days I want to feel a bit pulled together before I've even done my hair.
Keep it away from anything that bleeds. A denim jacket thrown over the top looks lovely in your head and leaves blue smudges on the cuffs by the second wearing, and don't sit on a park bench in it after rain, I learned that one the hard way on a bench that looked dry and clearly wasn't. The difference between a cheap set and a proper one shows up fast on white, because there's nowhere to hide a flaw. A good co-ord uses a fabric with a bit of weight to it, so it doesn't go see through the second you step into daylight, and a lining in the trousers or skirt so you're not performing a full risk assessment every time you bend over. Cheap white fabric is thin, slightly see through under shop lighting let alone sun, and goes grey in the wash within a month no matter what you do. Look at the stitching on the inside, a proper one finishes the seams so they don't fray, and the buttons feel like they'll survive more than three washes before they start shedding that cheap plastic sheen. Elastic waistbands on the trousers should have some give and some recovery, not the kind that goes slack after one sit down and stays that way.
Washing is the real test of commitment with white. Cold wash, always, separately, and skip the tumble dryer because heat sets in any mark you missed and yellows white fabric over time in a way you only notice once it's too late. A good quality one keeps its brightness through a proper handful of washes if you're sensible about stain removal straight away rather than leaving it in the laundry basket for a week, which I have absolutely done and regretted. The cheap version goes dingy by autumn and never really comes back, no matter how much you believe in the power of a decent detergent.
It's no good for the school run, for anything with small sticky hands nearby, or for a day where you know you'll be eating something with sauce, so be honest with yourself about the day you're having before you put it on. A white co-ord isn't practical and it was never trying to be, it's for the days you've got a bit of room to be careful.