If you gave me one small budget and told me to make somebody's wardrobe look different, I would not buy a garment. I would buy two belts and a scarf.

The reason is proportion. Almost every outfit that feels slightly off is a proportion problem rather than a garment problem, and a belt is a proportion tool. It puts a line where you want the eye to stop. It turns a shapeless dress into a shape, a long coat into a waist, a wide trouser into a deliberate one.

Scarves do the opposite job and are just as useful. They break up a look that arrived finished. A print at the neck of a plain outfit stops it reading as a copy of a plain outfit, and it costs a fraction of what a new top would.

These are also the pieces that survive weight change, seasons and taste changes, which makes them the least wasteful things in this whole batch.

Belts, and how to actually buy one. Width first: a narrow belt of two to three centimetres does a discreet line and works through trouser loops. A wider one at four centimetres and up becomes the feature and sits better at the natural waist over a dress or a coat.

Then look at the leather, because this is where price hides. A full-grain or top-grain strap has a visible finished edge, sometimes painted, sometimes burnished, and it will soften rather than crack. Bonded or corrected leather looks perfect in the shop and splits at the fold within a year. Turn the belt over: the back should be leather too, not a synthetic backing glued on.

Sizing is the part people get wrong. A belt is measured to the middle hole, and if you want to wear it high on the waist and low on the hip you need it long enough for both. Buy up a size and add a hole rather than buying two belts.

Vintage is genuinely better value here, and old buckles are usually heavier.

Scarves. The one thing worth knowing is that size and weight decide how it ties, and everything else is preference.

A ninety centimetre silk square is the classic and the most versatile: it knots at the neck, wraps a bag handle, or ties over the head without bulk. A narrow ribbon scarf is the cheapest change you can make to a shirt collar. A large wool or cashmere square works as a shawl and a blanket, and a fringed edge hides an imperfect fold.

For silk, look at the hem. A hand-rolled hem is a real marker of quality and you can see it: the edge is a small rounded tube rather than a flat machine stitch. For wool, weight and ply matter the same way they do in knitwear.

Hats and sunglasses are the third group because they are the fastest signature available. A hat you actually wear becomes yours within a month. Check the fit at the crown rather than the brim, and for sunglasses check that the frame does not sit on your cheek when you smile.