Go on Vinted, if you know the brands you like, search that, otherwise put in your size and put in 'cotton' 'linen' or whatever, and then find nice natural fabric outfits in key colours that you like depending on your preference. I think white and cream look good, black and navy, the odd pattern, but in the main don't buy any more polyester and don't buy printed stuff unless you absolutely love the pattern and can put it with something good (e.g. white t-shirt or shirt).
You can look around charity shops but they often aren't carrying recent stuff around here and so the jackets/trousers look a bit dated. I do still find the odd bargain though!
Leather shoes and bag (new or Vinted).
You won't necessarily look 'wealthy' but you will look well-put together.