I think the entire quote is worth reproducing in full:
Of course, there is really only one way of being perfectly dressed - that is, to be grossly rich. You may have exquisite discrimination and the elegance of a gigolo, but you can never rival the millionaire if he has even the faintest inclination towards smartness. He orders suits as you order collars, by the dozen. His valet wears them for the first three days so that they never look new, and confiscates them after three months so that they never look old. He basks in a perpetual high noon of bland magnificence.
It is useless to compete against him. If your object in choosing your clothes is to give an impression of wealth, you had far better adopt a pose of reckless dowdiness and spend your money in maintaining under a hat green and mildewed with age a cigar of fabulous proportions. If, however, you have no intention of deceit, but simply, for some reason, happen to like being well dressed, it is essential to have at least two tailors.
There are about a dozen first-rate tailors in London whose names you may always see quoted by the purveyors of ‘mis-fit’ clothing. Below them are about a hundred rather expensive eminently respectable unobtrusive shops in fashionable streets, where your uncles have bought their clothes since undergraduate days. Below them are several hundreds of quite cheap very busy little shops in the City and business quarters. The secret of being well dressed on a moderate income is to choose one of the first-rate and and one of the third-rate tailors and maintain a happy balance between them.
There are some things, an evening tail-coat for instance, which only a first-rate tailor can make. On the other hand, the difference between a pair of white flannel trousers costing five guineas in Savile Row or George Street and one costing two guineas in the Strand is practically negligible. The same applies to almost all country clothes. It is not necessary or particularly desirable that these, except of course the riding breeches, should be obtrusively well cut.
The chief disadvantage of small tailors is that they usually have such a very depressing selection of patterns. It is a good plan to buy all your tweeds direct from the mills in Scotland and to have them made up. Another disadvantage of the small tailor is that he never knows what is fashionable. At least once every eighteen months you should spend fifteen guineas in getting a suit in Savile Row, which will serve as a model for him.
It is never wise to allow any one except a first-rate tailor to attempt a double-breasted waistcoat; in some mysterious way this apparently simple garment is invariably a failure except in expert hands. But you can safely leave all trousers which are not part of a suit, even evening trousers, which ought, in any case, to be made of a rather heavier material than the coat, to our less expensive shop. The most magnificent-looking traveling coat I ever saw had been made up for four guineas from the owner’s own stuff by the second -best tailor in a cathedral town.
It is usually an economy to buy your hosiery at an expensive shop. It is essential that evening shirts and waistcoats should be made to your measure; cheap ties betray their origin in a very short time.
There is only one completely satisfactory sort of handkerchief - the thick squares of red and white cotton in which workmen carry their dinners. Socks wear out just as quickly whatever their quality, and are the one part of a man’s wardrobe which ought never to attract attention. Expensive shoes are a perfectly sound investment, particularly if you keep six or seven pairs and always put them on trees when they are not in use.
The strategy holds good even today, although I would argue that good-quality off-the-peg 'tailors' have largely (although by no means completely) replaced the sort of second-rate tailors that Waugh refers to. By the same token, I would tend to adapt his advice for today's gentleman and suggest that, if you are not a millionaire (or even close), you are well advised to find one very good bespoke tailor who you trust and can just about afford, and one or two good off-the-peg suppliers who you like and can more easily afford. As Waugh correctly says, there are many items of clothing that don't really justify top-quality tailoring. These days, I would suggest that unless you have a lot of money, flannel trousers might as well be bought from Ede and Ravenscroft or Roderick Charles rather than on Savile Row.
Likewise, Waugh has a point about country clothes. While a bespoke tweed jacket is a wonderful thing, you might feel that it is not the priority if you can only afford one or two bespoke jackets a year, and that a well-made off-the-peg one will do nearly as well.
So what should be bought from your tailor? Top of the list, as Waugh says, is evening wear. These days, this is more likely to be a dinner suit than an evening tailcoat, but the principle is sound. Even the finest off-the-peg dinner jacket will lack the elegant figure, clean lines and tailored waist that make such a difference to an evening suit. Better yet; since you will likely be wearing it relatively infrequently, it could easily last you a life-time and so is perhaps more palatable to a man on a budget about to spend a considerable sum of money with a tailor.
Whether you can have all your business suits tailor made depends entirely on your budget, but there is always a balance to be struck. There is no harm at all in buying the majority of ordinary grey and blue suits off-the-peg, and having just one or two suits tailor-made, perhaps in finer cloth or more unusual patterns.
The good news is that, perhaps unlike in Waugh's day, most men dress so appallingly badly that it no longer requires you to be a millionaire, or even wealthy at all, to look conspicuously better-dressed. The smallest modicum of good taste and care when buying clothes and getting dressed in the morning will lift you far above the crowd. These days, even the millionaires dress badly, as is unfailingly demonstrated every time a group of premiership footballers or hollywood actors assemble for an event.