As you get older and you don’t want to feel ‘meh’ (much prefer that term), I think it’s important to pretty-much plan your ‘outfit’ from head to toe no matter what you’re wearing it for.
This is as simple as chucking everything on your bed before you put it on to make sure that all of the colours/textures/tones go together.
Silhouette is VERY important and HAS to be up to date. No matter what you wear it’s important to understand where silhouette is up to (so general trouser shape/length, whether clothing is fitted/oversized/tight) and to echo this no matter what you wear. I mean wear what you want, but this is about avoiding feeling meh.
Then some minimal styling… so as PPs have said, an accessory, a coordinating bag, interesting shoes. But something, rather than nothing. And generally, try to stay away from the worst of cheap fabrics/very mass-produced, very ‘ordinary’ looking items. It’s less about how much things cost or where you buy them, but go for things with nicely set-in sleeves, patterns/stripes etc. that are well cut, an extra row of stitching on a hem, a touch of natural fibre in the fabric.
A smidge of attention to hair and makeup is also important… Hair in good condition/good cut helps (see point on silhouette above) but something ‘intentional’ looks great. Nothing wrong with splashing your face with water and scraping your hair back but this isn’t going to make you feel stylish. So a quick updo, a bit of mascara or lip gloss are always going to help.
Then suitability for the activity/conditions. Whether it’s gardening, taking the kids to soft play, attending a work conference… you’ve got to be temperature-appropriate and physically comfortable. No amount of badly fitting items, shivering/overheating, adjusting your knickers or wearing shoes that hurt is ever going to make you look and feel good.