First I have a disclaimer. I am an art supply junkie. I love just about every art tool made. Even a sharpened stick.
Simply put, you only need something to draw with and something to draw on. However, just having a paper and pencil might not allow you to have the best experience possible while you are urban sketching.
Many people like to sketch with pencil first so that they have the ability to erase mistakes or change the way they first drew something. If you’re using a pencil just to lay down the foundations of your artwork, any pencil should do. However, if you want to only use pencil for your artwork, you should be aware of the types of pencils available and which one would best for you. I have grown fond of a mechanical pencil Pentel makes. The Graphgear 1000, .07 lead. The clip retracts the lead. Genius! They feel great in your hand.
If you want to really have fun, explore fountain pens! Check out Goulet Pens and Jet Pens on line. Fountain pen stores are few and far between. Fortunately we have one here in Kansas City, The Pen Palace. We also have a fountain pen club that meets once a month. They are a wealth of information. Someone usually brings part of their collection to show and sometimes one will be for sale.
The old fashion fountain pen is fabulous to draw with. Parka Blog has several great reviews to tease you. Liz Steel’s blog also has a wealth of information for sketching pens at affordable prices. Liz is one of the Craftsy instructors as well. Fountain pens could be one entire blog, and there are many out ‘there’.
Sakura Micron Pens are waterproof, archival ink. This ink is also chemical-resistant, fade-resistant, bleed free and quick-drying as well. The waterproof quality also helps if you want to add watercolor to your sketch. These pens are also available in a variety of different sizes. (0.2-mm, 0.25-mm, 0.3-mm, 0.35-mm, 0.45-mm, 0.5-mm) and a brush and graphic tip too! There are several brands to chose from. Pentel, Coptic, and others. Do your research to select pens that fits your needs. (Note that’s a plural… Pens.)
If you want to add color, you have lots to chose from depending on the ground you are working on. Colored pencils, water colored pencils, pastel, markers, inks, acrylic and watercolors to name several options. Watercolor is my first choice. I reasearched extensively and found Jane Blundell to have one of the best informative blogs. She has created volumes of research on watercolors.