Aim for a capsule wardrobe, a few neutral basics & swap out a clutch of tops/plain fitted tee shirts until you can afford more. No need for suits or expensive dresses.
Keep everything pristine, polished & well pressed, you’ll look like a minimalist professional.
A pair or two of plain black or navy trousers with a bit of Lycra so they don’t bag or crease, & can go in the machine once/twice a week.
Plain black ankle ankle boots, bit of a heel, polished every morning.
Plain neutral wool mix (so machine washable) thin jumper & a cardi -black/grey/navy & another shade for colour pop.
Several white/neutral tee shirts that fit & flatter.
Couple of plain fitted shirts - bit of Lycra to keep shape - to match trousers & another for pop of colour.
Thin black ankle socks/trouser pop socks - everyday socks are a giveaway when trouser legs ride up.
Pick out & treat yourself to a lightweight flattering scarf that you can wear during the day for style & warmth.
All this you can get as a co-ordinated shop at Next/M&S/JohnLewis/Gap etc.
You can wear this collection, circulating the trousers & tops, for a few months until the spring/summer colours come in & you can afford more. If you need a work bag, keep it plain & simple, some mock leather bags are very stylish & not ££.
An easy update is to work out which seasonal new colour suits you & grab a few items from M&S to ‘refresh’ your look. M&S usually has a simple button up cardi/linen shirt/tee & shirts in most of the new colours.
Less is more.