The advice above is all great. I lost my way and am just getting back on track, following similar ideas.
Simple, flattering colour palette. Black, navy, grey, plum are good. But it does depend on your colouring. It's easy to work out what works though(try Pinterest)
Minimalist but good jewellery. For me, it's pearl earrings (diamond studs on a good day), a nice watch, a silver bangle, diamond necklace. Not all at once.
Choose a couple of styles that make you feel good and plan your outfits around these. Like others, I like skinnies and a loose knit. I choose knee high boots and have invested in a couple of good coats (a black belted Barbour and a Navy wool coat). I also really like above the knee dresses and have a few in different colours. These can be really good as they can be as smart or as casual as you want them to be. Dresses are a complete outfit, so as long as it looks nice, that's the job done.
Ignore fashion, wear what makes you feel good. However fashionable they got, there weren't many chic Parisians in cold-shoulder tops.
Once you get your makeup and hair sorted and everything else looks much, much better.
I like a bit of 'quirk' but fit it into a more 'chic' outfit. So, perhaps a pair of unusual tights or a necklace found on travels overseas.