A friend from the fashion industry's distilled and mostly-verbatim wisdom:
Learn what expensive fabric feels like. Have a friend buy you 4 price tiers of clothing with the exact same fabric composition; try them on blindfolded. Focus on fabric only, not fit. At some price point you will stop feeling a difference. There's no reason to pay for what you can't feel.
A 100-dollar shirt tailored for 30 dollars exceeds a 500-dollar shirt in appearance but not in feel.
A hoodie is a hoodie at any price point.
All denim looks identical. Jeans that are the exception to this rule usually come from smaller makers, usually cost over 250 dollars, and usually last 5 to 7 years, and will look best midway through its life when the way in which the threads wear betrays its quality, like a proper Persian rug.
A 200-dollar suit is like a paper bag, no matter your tailor.
Your tailor is your shirt's second-best friend. Your shirt's best friend is diet and exercise.
If you dress too similarly to your colleagues, you are a school of fish. If you dress too differently, you are a shark, or a squid, or some other thing. Neither of these is a great idea.
Never mention the brand of your clothing. Ever. Seriously.
A logo is a brand's way of forcing you to mention them.
And finally, my favorite:
Look on the street. Nearly everyone is wearing something boring. And everyone got up in the morning and looked in the mirror and thought, "this is okay." If you saw one of my models walking along the street before we shoot, they would be the same! — except they're wearing beauty, also. But nobody believes buying the clothes could ever make you look that way. So that can't be what we're selling, no? What we are doing is taking a beautiful human and deciding what furniture to place them on, how to adjust their posture and expression, what country we'll be in, the exact hour of day, whether our photographer makes it all seem triumphant or melancholy or joyful or pensive. There must be some art to it, or everyone on the street would walk around looking as though they are moving from frame to frame in a series of friezes, and no one would pay me. You even know you are buying a fantasy from me, don't you? [Sure.] And can you tell me what that fantasy is? Not beauty... even the model's beauty is in service to, the idea that for a moment, everything in life falls into this perfect kind of space, some harmony... So to be stylish is to both take all this constantly in the same moment you appear that these things do not even exist to you — that you are as you might find a bird perched in a tree, just being, and meanwhile God smiled a beautiful poetry upon you. But I am guessing this is not the recommendation you were looking for.