Have a look at Brittany Bathgate on YouTube. She almost always wears a jumper
And trousers but is very stylish and minimalist. She wears a lot of Cos/Arkett/Uniqlo as well as more expensive brands.
I know a few architects and interior designers and they all dress in a very understated way. Really well cut clothes in a limited colour palette. No polyester, bright colours or prints.
Build yourself a capsule wardrobe for work. Choose 2/3 colours that work together, I would go for navy/charcoal/white with accents of olive green and dusky pink because they are colours that suit me and work well together. Think about the colours you are drawn too and that light up your face.
I would start with something like:
I pair of wide leg trousers in charcoal
I pair of slim leg ankle grazers in navy
A good white shirt or blouse
A good white t shirt
Cashmere or merino jumper in navy/grey/olive
The best blazer you can afford, they have transformative powers. Make sure it fits really well on the shoulders.
A classic pair of leather shoes, something like brogues, they go with everything
Look in Uniqlo, Cos, Mango, Massimo Dutti, Zara, Kin, And/Or from John Lewis. Search for them on eBay too if you have the time/patience
Keep it simple and everything will go together. Those pieces will give you a week of outfits and then you can add in more as you go. Stick with classics, a trench coat, a dress, a well cut denim jumpsuit maybe. Make sure that anything new that you buy works with what you've already got.
I'd try and get is a good leather bag. I appreciate you don't have a designer budget now, so go for something minimal and underrated, Cos or Arket should have something that fits the bill.
Good luck with the job hunting!