An essential is defined by utility, not by quality or price: a garment earns the label if removing it would cost you several outfits.
That makes published essentials lists unreliable. A blazer is essential in one job and worn twice a year in another; a trench coat is a cornerstone in a mild wet climate and useless in a cold dry one.
Derive your own from two weeks of recording what you actually wear. Pieces that appear three or more times, and have no substitute, are your real essentials — and the ones worth owning twice.