Proportion is doing more work than price
The same outfit at two different proportions reads as two different price points. This is the part that transfers across every budget.
A recurring observation in fashion commentary is that some people look expensive in inexpensive clothes. The explanation is usually given as taste, which is not actionable. The more useful explanation is proportion, which is.
Where the eye stops
An outfit creates horizontal lines at every point where one garment ends. Hem, cuff, waistband, shoulder seam, boot shaft. Each of those lines tells the eye to stop, and the placement of those stops is what creates the impression of height, balance and deliberateness.
Cheap-looking outfits are frequently outfits with too many stops placed too close together. Three lines within a hand's width across the torso will fragment a silhouette regardless of what the garments cost.
The one-third rule, and when to break it
Dividing a look roughly one-third to two-thirds — rather than in half — reliably reads as more considered. A cropped jacket over a long skirt does this. A tucked shirt with high-rise trousers does this. An untucked mid-length shirt over mid-rise trousers halves the body, which is the least flattering division available.
The exception is a deliberate column: a single unbroken colour from shoulder to shoe, where there is effectively one long section and the rule does not apply. Columns work precisely because they remove stops rather than placing them well.
Volume needs an answer
Volume in one place needs restraint in another. A wide trouser with an oversized knit is not balanced; it is two statements competing. The same trouser with something fitted above resolves immediately.
This is the cheapest correction available in any wardrobe, because it requires no purchase — only a different pairing of things already owned.
Where fit actually matters
Shoulder seam placement on outerwear, trouser break at the shoe, and sleeve length are the three fit points most visible to an observer. They are also the three most commonly wrong on inexpensive garments, and the three most easily corrected by alteration.
Spending on alteration rather than on the next garment is consistently the higher-return decision, and it is the one most often skipped.