Jeans have had a proper shake up in the last decade, and mostly for the better. The stretch in a lot of denim now is genuinely good stretch, the kind that moves with you rather than bagging out at the knee by lunchtime, and the range of cuts on the high street means you're no longer stuck choosing between skinny and skinny. Wide leg and straight leg have come back properly, not as a trend that vanishes in a year, and that's made it easier for more body shapes to find something that actually sits right at the waist and hip.
A good pair earns its place by going quietly into things you already own rather than demanding anything new. Blue jeans with a plain jumper and trainers is the one you'll reach for on a Tuesday without thinking. Black jeans do the same job but read slightly smarter, so they'll go under a blazer for a work thing or with boots and a coat in the evening without you having to change twice. A simple white shirt works with almost any cut you choose, tucked in for the straighter legs, left loose over the slimmer ones. Build around two or three tops you already wear on rotation and the jeans will carry more of the week than you'd expect.
If you're starting from nothing, a mid blue straight leg in a decent stretch denim is the sensible first buy. It's forgiving through the hip and thigh, it doesn't date the way a very skinny or very wide cut can, and it sits well with most shoes, flat or heeled. From there you can add a black pair for the days you want something that looks a bit more pulled together with no extra effort.
Denim with real cotton content ages well, softening and fading gently at the seams and the backs of the knees in a way that looks lived in rather than worn out. Wash it less than you think you need to, inside out, on a cool setting, and skip the tumble dryer if you can, since heat is what kills the stretch and makes a pair go slack in the seat within a few months. Treated that way, a good pair will see you through at least a couple of years of regular wear.
They're suited to almost any time of year and most ordinary occasions, weekends, the school run, casual dinners, a daytime that turns into an evening. The one place they properly fall short is anything with a strict dress code, a wedding or a formal work event, where no amount of good denim will do the job a dress or trousers in proper fabric would.