Start with versatility. Two or three pairs of trousers, several tops or shirts, one good blazer, comfortable professional shoes, and a bag that works for commuting or travel can cover a surprising number of situations.
Fit matters more than brand. Use the consulting dress-code baseline to decide what looks appropriate, then buy slowly rather than trying to create a complete wardrobe in one weekend.
Spend where discomfort becomes expensive: shoes, outerwear, and anything you will wear repeatedly while traveling. Save on trend-driven pieces and duplicates until you know what your office actually wears.