Seriously, start with footwear. Polishing up a very old pair of scuffed smarter shoes won’t impress. A fresh, squeaky clean new pair of brogues however, will.
Going for an interview in an office that doesn’t require a suit and tie? Try some smart, fitted knitwear over a crisp shirt. It looks just as smart and professional.
Usually you won’t be required to turn up with heaps of paperwork but you will be expected to turn up with at least a CV. House that in a smart satchel. Beats an old backpack any day.
Going somewhere quite formal for an interview? Wear a waistcoat under your suit. This will add a dapper twist. Or, if you are interviewing somewhere a little more casual try a waistcoat over your shirt.