The dos and don’ts of office attire, according to 2 professional stylists

This is the piece of professional clothing you need to invest in

Not entirely sure what to wear on the first day of a job or to that important meeting where you ask for a promotion? Workplace stylists Jacci Jaye and Alexandra Suzanne Greenawalt have you covered.

In conversations with CNBC Make It, both stylists offered up what you should - and definitely should not - spend your money on in order present your best self.

Here's what you should buy immediately

Jaye tells CNBC Make It that the one item professionals should invest in is a custom suit. She says that custom suits are tailored to fit to your specific dimensions, which flatters your body type and exudes a more polished look.

Though custom suits have a reputation of being expensive, Jaye says that their price has fallen in recent years as the market for them has become increasingly saturated.

"Sometimes you'll find there isn't much of a price difference between a custom suit and one you buy off the rack," says Jaye. "So you might as well invest in one that's custom."

However, if you do choose to purchase a suit off the rack she emphasizes that it should be tailored, because fit trumps cost. An expensive suit can look very cheap if it's not tailored properly, she says, and a cheaper suit can look pricier if it fits well.

Although many women still wear pantsuits, think Hillary Clinton, it is no longer de rigueur, says Greenawalt.

Easy ways to make your casual clothes appropriate for the office

In place of the "power pant suit," she suggests that women wear dresses or a dress paired with a matching jacket. In fact, the stylist admits that she usually takes outdated pant suits out of her clients closets because they are not "modern or flattering."

Women who opt for dresses or skirts should make sure they are no shorter than two inches above the knee and should purchase proper shape wear, which sleeks and slims the body, says Jaye. She adds that hosiery should always be worn. "No bare legs."

For an executive casual look, a la Silicon Valley, Jaye suggests that men wear a button down shirt with a blazer, paired with nice trousers and loafers.

ML Harris | Image Bank | Getty Images

Here are the fashion choice to avoid

Greenawalt says her biggest workplace don'ts are dressing too sexy or provocatively, wearing too tight or too loose clothing, items that are stained or have holes, sweatpants and casual shorts or t-shirts.

Jaye adds to that list: distressed or light colored denim, flip-flops, sneakers, hoodies and clothes with logos or neon colors.

"Ask yourself, what purpose does this clothing serve?" Jaye tells CNBC Make It. "Flip-flops have a purpose for the beach. Gym sneakers have a purpose for the gym."

If you cannot part from your jeans, she suggests wearing a pair that's dark denim and nice fitting.

Jaye adds that executives should not wear open-toed shoes. Men in particular should wear low-step shoes with suits and all clothing items should be pressed and wrinkle-free. Polos are also frowned down upon, says the stylist: "You need to keep that formality."

Greenawalt says that dressing well not only boosts your confidence but shows how you want to be perceived.

Jaye agrees, saying: "People judge character based on what you're wearing.Your style tells people how reliable you are and how respectful you are to yourself."

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