I found an M&S silhouette of trousers that works for me and I have 2 navy and 2 black pairs, and a similar style but heavier pair (so feel more suit-like) from Hobbs.
I started with a LandsEnd style of long sleeved top, and got a whole bunch in navy, black, white, red, pine green, turquoise etc. But over time, I prefer M&S boatneck style with 3/4 sleeves and I needed to replace tops, I've been swooping those in instead(and a couple of the same neckline but sleeveless for summer). And a couple of Hobbs silk tops for variety. And for winter, I have some plain round neck jumpers that can be on their own for more casual days or under a jacket for more formal days but warmer than the tops.
I have 2 Hobbs wool jackets (cobalt blue and purple), an emerald green one, a navy Boucle, a black boucle, a navy/burgundy mix boule, and 2 linen from M&S for summer (pink and navy). Add in a good handful of various silk and wool scarves and some statement jewellery (necklaces or brooches for the jackets).
So I pick a base colour (black or navy), a jacket and then a top that works with those colours. Very similar "uniform" daily, but different colours and variety of how they mix together, and some variety in my jacket shapes and materials. And add an accessory some days but have a few options.
I have a relatively good choice of options without having a massive wardrobe. And change flat shoes in summer for boots in winter.