During her job interview with Net-a-Porterfounder Natalie Massenet, Stephanie Phair—now the director of Ms. Massenet's discount spinoff site, the Outnet—got the best compliment one girl in fashion can pay another: "Where did you get your outfit?" Sonia Rykiel skirt? Loehmann's. Dolce & Gabbana heels? Sample sale. "It was totally by chance," recalled the 32-year-old Briton. "I don't know if that's what sealed the deal but I was able to convince Natalie I walked the walk." Ms. Phair's keen eye and lifelong high-low approach to dressing has made the Outnet the best-edited online destination for women shoppers of all tax brackets. Since its launch in 2009, the site has provided a global clientele with a curated stock of rarely slashed cult brands like Alaïa, Céline and Balmain. (If you're lucky, a Burberry Prorsum taffeta trench can be yours for 70% off.) The Outnet has remained impervious to the economic downturn, flaunting the same aesthetic as its older sibling with a bounty of high-end sale stock, where customers can view completely styled outfits from a range of past collections (seasons are deliberately not listed on the site) with nicknames like "Tea at the Plaza" or "Hip Berlin."
With a pedigree that includes Oxford and a three-year stint in the public-relations and marketing department at American Vogue, the "designer agnostic" is a veteran when it comes to looking good for less. "If you're going to buy designer, play to their strengths," the Knightsbridge resident advised. "Buy something in that signature Valentino red or something tailored from McQueen. Then buy a sweatshirt from Gap because that's what they do well." For her own daily uniform? Ms. Phair relies on her McQ skinny trousers, Paul & Joe blazers and Rick Owens motorcycle jackets when flitting about the globe discovering everything from Uruguayan rancher boots to knickknacks at Japan's ¥100 shops ("The equivalent of a $1 store full of quirky gadgets"). Here, she reveals the few things in life she'll splurge on and, most importantly, her well-guarded bargain shopping secrets.
The best flea markets are in Forte dei Marmi, an Italian beach town near Pisa, where I bought an amazing snakeskin handbag for €200 [$284]. In Buenos Aires, San Telmo has beautiful antiques, from silver cutlery sets to old frames. Somehow all the belongings from turn-of-the-century wealthy families have found their way to these markets. Afterward, you can stop in a confiteria to have a coffee and a toasted sandwich with tango music playing outside. In Paris, there are a number of covered markets at Clignancourt—just don't try to do it all at once, that's a big mistake. My favorite is Marché Serpette. The stall owners are true aficionados, so you can still find antiques at a good price.
I am obsessed with this little shoe shop at the very bottom of the stairs in Positano called Tre Denari that sells little leather loafers in every color of the rainbow. The craftsmanship in Italy is so great. They don't have a phone number and don't appear on Google. You can buy multiple pairs in crazy colors because they're only €30. They're amazing to slip on for a flight.
My best find on Craigslist was a 1930s high chest for $250. It was valued by an antiquarian at over $4,000. A lot of people who use the site are in the middle of moving, so they're desperate to get rid of their pieces. It's always the best place to find well-priced furniture.
I always incorporate vintage into my wardrobe. In London, I just rediscovered Alfies market in Marylebone, and in New York, 25th Street has great vintage dealers. It also has a few closed-in markets, like the Showplace. Years ago, I bought a 1950s white beaded cocktail dress but never had the opportunity to wear it because it always made me look like a bride. Five years later, I wore it to my own wedding!
The most storied place to find Gaucho boots is Casa Fagliano, a hole-in-the-wall bootmaker in Hurlingham, which is a British suburb of Buenos Aires. He has outfitted royalty, as well as polo players. I wear them with short skirts or skinny jeans.
For certain things, I go to the source. Argan oil is only available in Morocco and a lot of beauty brands are using it as their new secret antiwrinkle ingredient. A year ago, my then-boyfriend and I were driving through the Atlas Mountains and saw a sign for a women's cooperative just before the Toubkal National Park. It's a microfinance operation where all the women make the oil, so we stocked up on the real deal.
I'm mildly addicted to Gwyneth Paltrow's website, GOOP. She recently did a story on French pharmacies, which I go to for La Roche-Posay Micellar Solution, the French equivalent of Cetaphil. I also love Nuxe gold-flecked body oil, which isn't that expensive but it's totally an indulgence because frankly, no one needs gold body oil.
I never leave home without Lucas's Papaw Ointment. It's the Kiehl's lip balm of Australia. We have quite a few Aussies who work at the Outnet and they've made everyone addicted.
Department-store culture in Japan is unbelievable. Their basements are reserved for hundreds of stalls selling weird and wonderful foods in beautiful, eye-catching packaging. Mitsukoshi in Ginza is Japan's oldest. I go when the store opens to watch the amazing ritual of the staff welcoming guests.
For travel, I go to i-escape.com. They sort hotels by price and have unique little family-owned hotels like the Bon Ton on the island of Langkawi in Malaysia. The houses are actual old 18th-century Malay homes on stilts, so you are staying in a piece of history.
I splurge on food. I won't spend £100 [$161] on certain things but I have no trouble booking myself into the new Heston Blumenthal restaurant for a tasting. When it comes to a proper meal, I have a completely disproportionate sense of value.—Edited from an interview by Nicole Berrie