When you are getting dressed in New York, you sort of have to dress for a variety of different things; for your walk to the subway, for your subway ride, for the office, which may have the A/C blasting or maybe the heat blasting. One of the easiest ways to deal with these varieties of temperatures is to layer. The first lesson in layering is to make sure that every layer fits really, really well.
Layering is a great way to bring a ton of different looks and styles into your outfit but you want to make sure that you do not look like you are wearing ten different layers of clothing. So it is all about making sure they fit. Your bottom layer should be as clean and close to the body as possible. Then if you are wearing a cardigan, it should not be a giant oversized cardigan. Maybe pair a snug cardigan and then a blazer over it with a scarf, and right there you have three or four layers and you are still going to look very clean and very fitted and you are not going to look sloppy.
Another really easy way to layer without looking like you have a ton of different things on is to keep things in the same color scheme. So maybe wear a lot of black and gray together. Or if you are doing browns wear a camel with a darker chocolate brown. That is an easy way to look neutral and streamlined without looking bulky.
If you are going to stay in the monochromatic look, mix in different textures. If you want to wear all black, I think that is great. It is an easy way to do your wardrobe; you do not have to think about it. Try and mix in different textures so that it still looks interesting. If you are wearing black denim then maybe wear a silk blouse and then a big chunky cardigan or a linen blazer that has a nice texture to it and then a silk scarf.
If you are wearing a ton of different textures, maybe pair that with a really good leather bag. The best way is to keep things in the same color scheme but make sure there are different things going on in each of the layers. That way everything is interesting and you do not just look very bulky.
Another way is to bring color in via one element. If you are wearing all black, wear some bright red shoes. Or carry a yellow bag. Or a green bag. It is really surprising and it is eye-catching. It is an easy way to make something feel different, especially when you are wearing the same clothes all the time because it is cold and you fall into that style rut. Accessorize. Wear earrings or jewelry, that is where you bring some color and some interesting looks to your layers.