Work:
Smart black or dark grey jacket or navy or blazer(s)
Smart black, dark grey, or navy skirt(s)
Tailored black trousers (or grey or navy)
Practical leather shoes (I'll be glad when the high heel in office nonsense has finally had its day and been left in the 1990s where it belongs - in previous jobs you could always tell the bought-in management consultants by the way they'd teeter about on the gravel on their little kitten heels, not to mention the shiny hospital floors...)
White or pale pastel colour shirt
Plain tights, black, nearly black, or flesh coloured as appropriate
Maybe a couple of shift dresses in practical dark colours or beige and cut in a style that allows you to work (depending on what your job is)
Good underwear (I'm now [young] granny age so personally I like cover-me-up Bridget Jones knickers). And a decent bra makes all the difference.
Good bag
Black umbrella
This might all sound a bit drab, but you can pretty it up with cardigants or scarves and earrings and pendants or necklaces, depending on the environment you work in and what the current fashion is
Outside work:
Little black dress
Pretty dress or two in a colour or pattern and style that suits you, in case you get an unexpected party invite (remember those?!)
Nice strappy sandals (with a heel you can manage to walk in)
Pretty bolero or cardi little jacket to match pretty dress
Holiday clothes - depends where you're going, but a good swimsuit, a nice cover up to avoid sunburn, and jeans or practical trousers and Tshirts or tops and shoes so you can enjoy walking about as a tourist (if it's safe), plus a hat of some description and a crossover bag.
And if you're going ski-ing in Switzerland, or hiking in the Cairngorms, good base layers and waterproofs and hiking boots. And maybe a beekeeper's suit if you're anywhere near Scottish midges. (Or that's possibly just me.)
I had one boss in her late 50s who really still seemed to think she was 22. In fact, she wore things I'd not have felt comfortable in at 22. So please, no leather skirts or fishnets in the office!!
If you're just building your wardrobe, I've often found you can pick up excellent, long-lasting labels on ebay or vinted or, when they're open again, in charity shops, especially in the more well-to-do areas. Our local hospice shop is amazing. I've just admitted I need to say goodbye to my lovely North Face snuggly raincoat as it's come to the end of its natural life - that was a charity shop bargain about 8 years ago. I've also found it's a good idea to work out what colours and styles really work for you, within the constraints of fashion when you're buying - one tip I was given years ago by someone who did colour me beautiful type stuff was to hold a white sheet under your chin and then hold up different coloured garments so you could see which ones really suited you.