"a popular way of dressing during a particular time or among a particular group of people; the business of creating and selling clothes in new styles; clothes that are popular."
The debate between what is fashion verses what is style is a direct result of the fact the definition of fashion itself is flawed and incomplete. Fashion cannot exist without style, just as style cannot exist without fashion.
No different to art, music, and literature, fashion is a form of self expression shaped by our own human experiences. It should not be defined by the level of "popularity" it experiences in a given time period, nor should it be justified by the opinions of anyone but your own.
It is ridiculous to equate fashion by current trends, or how much you "buy". Defining fashion based on trends, popularity or the "business" that exists around it, takes away from the artistic nature of fashion itself.
Fashion does not discriminate and anyone who has the courage to embrace who they are, is capable of fashion. Letting go of the desire to be accepted and following what socially surrounds them, is one of the greatest challenges in life.
Fashion is not simply the physical adorning of the body, face, and hair, but the collaboration of the inner thoughts, and personal taste that allow you to create your own self-presentation. If you simply dress without thought, the garments you wear, will always remain as lifeless textile.
Any worthy fashion designer, has a vision, and a message inspired by something. Copying head to toe looks, created by a famous fashion house, is undoubtedly a sure way to impress and look flawless. However, it should not be mistaken as your own merits of fashion, you are merely a dress form, displaying the fashion abilities of someone else. If you steal fashion to your benefit, it will surely use you right back.