Wear All Black
There's a reason New Yorkers are always praised for being so stylish: They wear all black, all the time. It's simply impossible to not look chic in fashion's favorite color, and it literally will never go out of style.
You don't need to get fancy. Throw on a pair of black leggings and a black t-shirt. Promise you, you'll feel much more put together than if you had on a million mismatched colors. And hey, black hides spit-up the best.