As said, no. No spell can change your DNA I'm afraid, you are human. Real magick is similar to prayer, you focus on a desired goal, then work to achieve the goal [there's more to it, but that's basically it. You focus nature energy on a specific path to bring a desired change. This change cannot contradict nature however as the energy is part of nature]
Now, regarding the reason why magick cannot turn you into a faerie I suggest you use your common sense. Take a step back, read this 'spell' and ask questions. [Should I drink glitter comes to mind] while belief in a spell is important you should also understand the spell, if some ingredients or steps in casting seem off to you, research and ask questions. [Also, not all potions are meant to be consumed, some are, others are to be worn, bathed in, carried in a bottle, so on. Potions are simply liquid spells, so anything from teas to soup, oils to lotions are considered potions]
That all said, faeries are real [well it's a strong held belief to many] they are like spirits of the earth, they are not like most faeries tales depict however, some are quite ugly and malicious. They aren't all tiny dainty humans with butterfly wings who sit on a mushroom and look sweet. They can be, but they can also be quite mean and vengeful. If you would like try looking into Fae magick and working with faeries.