In His 20s
Whether post-college or early career, men in their 20s should own a well-cut, well-fitting dark suit. Whether you work in a profession where you wear a suit every day or whether you only wear it for weddings and funerals, you will wear it. A classic suit will last for decades, so this is a good place to spend a little extra and buy high quality. And don't forget a few crisp white dress shirts and a couple of good neckties. And learn to tie a proper Windsor knot.
Along with a good suit, every 20-something male should own a good pair of leather dress shoes. They can be worn with the suit, but they also look much better than old sneakers or casual shoes with everything from jeans to khakis to dress pants. Good quality, well-polished leather shoes are a great polishing touch on any outfit. And don't forget a matching leather belt.
By the time a man is in his 20s, he should have a passport. These are your years of freedom to travel. You never know when you'll get the sudden opportunity to visit Spain, or Italy, or Scotland, or Zimbabwe. Don't miss that opportunity because you're not prepared. And if you don't get the opportunity, make it.
For slightly less formal occasions than those calling for a suit, invest in a cashmere V-neck sweater: navy, baby blue, brown, dark green, black, grey. You can pair it with a dress shirt, dress pants, and a necktie for a business meeting or toss it on with jeans for a more casual bar outing. Believe me, if you wear a cashmere sweater to a bar, women will find a reason to come touch your arm.
This may sound sexist, but every man in his 20s should own either a good Swiss Army knife or a Leatherman tool. You're a man; you're expected to fix stuff. Just accept it. And with either one of those two items on hand, you will be able to open a bottle of wine, cut your own kindling, unscrew a broken lightbulb, tighten a wobbly table leg, clean your nails, and otherwise address any emergency that might arise.
In His 30s
Similar to women, a man in his 30s is likely to be both raising a family and developing a career. He has more disposable income and hopefully a few more upscale pastimes. Which is why the first thing a man in his 30s should own is a nice set of luggage. Whether for business travel, a family vacation, or a romantic getaway for two, a set of sturdy luggage including an overnight rollerbag, a garment bag with a shoulder strap, and a full-sized suitcase is a must.
A mistake that many young men make is carrying a large wallet. It looks messy, takes up too much space, and it's bad for your back to carry it in your back pocket. You rarely need everything that's packed in your wallet anyway, so lighten your load by carrying an elegant money clip. Personalize it by getting one with the logo of your company or an organization you volunteer for, an engraved monogram, or even your or your child's birthstone.
Another great way to show your personal style in your 30s is with a great pair of dressy cufflinks. Brushed silver, textured gold, mother-of-pearl, a logo or symbol of something important to you. And of course, what's the point of cufflinks without a great dress shirt with French cuffs to wear them in?
Speaking of disposable income, a man in his 30s should have an investment advisor. Finances are more complicated than they've ever been, so unless you're in the business yourself, let someone do the financial legwork for you.
The final thing that a man in his 30s should own - if he doesn't already - is a "new" car. Not necessarily a brand new, fresh from the factory, never-owned car, but a reliable, good condition, well-maintained vehicle which never previously belonged to a family member, and which came with some kind of dealer warranty. And he should maintain it religiously.
In His 40s
Much like a tuxedo, a well-tailored, classic wool or cashmere dress coat makes every man look good. In your 40s, this is the time to add such a coat to your wardrobe. You're sure to make an impression walking into a business meeting or networking event wearing a great coat. A classic style dress coat, if taken care of, will literally last for the rest of your life, so this is an investment. Don't skimp. And don't forget a good pair of leather gloves to go with it.
I'm a big proponent of hats - not just any kind of hats, but GOOD hats - so I recommend that any man in his 40s own a good hat. It can be a Greek fisherman's cap, a jaunty fedora, even a well-made cowboy hat. But it should be something that makes you feel confident. A great hat will get you noticed, and your 40s is when you have the poise and confidence to pull it off. Just don't forget that a gentleman never wears a hat indoors.
A man in his 40s should also be able to host a good party, and what party is complete without a bar of some kind? Even if you don't drink alcohol, it's nice to be able to offer your guests elegant mocktails and non-alcoholic drinks. You should own several sizes of cocktail shakers and strainers, various styles of glasses (red wine, white wine, highballs, beer mugs, martini glasses, etc.), swizzle sticks, an ice bucket, bottle openers (a Rabbit is the best), and a compact bartender's guide.
Although cell phones have made watches less common than in years past, a watch is an elegant and classic piece of jewelry, and every man in his 40s should own a nice watch. It doesn't have to be a Rolex, but it shouldn't be a Timex, either. Tissot, Tag Hauer, and Movado all make gorgeous, affordable watches that can become heirlooms passed down to future generations.
Handwritten correspondence is also less common than in the past, but that's no excuse for not having a really good pen for those occasions when writing is the way to go. A man in his 40s should own a really good pen, preferably a fountain pen. It's not just a pen, it's a work of art.
In His 50s
By the time a man is in his 50s, he probably has at least one well-established hobby. It could be anything from fishing to tennis to chess to golf. When you're in your 50s is the time to invest in some good quality equipment for whatever it is you do in your spare time. A high-end fishing rod, an expensive tennis racket, a hand-carved chess set, a professional set of golf clubs, even a motorboat or a motorcycle - just think about what you love doing and invest in it.
By the time most men are in their 50s, their children are old enough that it's safe to invest in good furniture. So, like Archie Bunker, now is the time to get yourself a really comfortable chair that's all yours. A leather armchair, a La-Z-Boy recliner, a soft overstuffed chair, whatever appeals to you.
By your 50s, you should own at least one musical instrument that you know how to play: a piano, a harmonica, a guitar, a drum set, a penny whistle. If you don't know how to play anything, learn. Take paid lessons, pick it up from a friend, buy a book and teach yourself. But learn to play something, even if you never play for anyone other than yourself. It's a great way to relax. And it's also a great way to liven up a boring party.
Every man in his 50s should own at least one piece of original art - not merely as an investment, but something that you enjoy for its pure aesthetic value. It could be a sculpture, a painting, a print, even a first edition book. But it should be something that speaks to you, something you enjoy looking at or touching. Bonus points if there's a good story of how or where you got it.
That's my take on men's essentials at various ages. For the record, my husband just turned 50, and he has a beautiful woolen greatcoat and leather gloves, several good hats, an absurdly well-stocked bar (liquor as well as barware), and a nice watch. He is, however, lacking a fountain pen, a situation I intend to rectify very soon.