The moment it clicked was a grey Sunday in October, come to think of it, a plain charcoal jogger and a sweatshirt that matched closely enough nobody could tell I hadn't planned it. I'd worn joggers for years as the thing you put on after the real clothes came off, and suddenly here was an outfit that looked like a decision rather than a surrender.
If you've got none of this in your cupboard, start with a matching set in a mid weight cotton blend rather than anything shiny or technical looking. A proper tracksuit, jogger and sweatshirt cut from the same fabric, does more for you than two separate pieces bought on different days that never quite sit the same way. The jogger should taper gently rather than cling, because a skinny cut through the ankle reads as leggings pretending, and a wide leg one reads as pyjamas that got lost on the way out. Once you've got one set that fits properly you'll know what you're chasing when you add to it, and it's much easier to judge a bold colour or a cropped length against something you already trust.
Before you buy, check the cuff and the waistband before anything else, because that's where cheap ones give themselves away first. A ribbed cuff that's gone slack after one wash will flap round your ankle for the rest of its life, and a waistband with no proper elastic core will roll over the second you sit down, which, with joggers, is rather often the whole point. Have a proper look at the drawstring too, there's nothing more irritating than losing one inside the waistband in week two and spending ten minutes fishing it back out with a safety pin. Pockets with a working zip are worth the extra look if you're going to use them for a phone or keys, and a longer length saves you from that half mast look once the fabric relaxes with washing. Weight matters with the seasons, a lighter jersey earns its place from spring through a mild autumn, while anything brushed or fleece backed is really a winter piece and feels clammy the second the weather turns.
For colours, I've had far more luck with charcoal, navy and a proper dark bottle green than anything pale, which shows every crease and every dog hair within the hour. A soft, slightly dusty tone sits better over years than true black, which goes grey at the knees long before the rest gives up.
Would I still reach for this on a day I actually had to leave the house, or only on one I didn't?