With a photo or two attached I could probably make some more exact product recommendations for you but, for illumination on a deck most homeowners prefer subtle light output in general. Surface mounted deck lights are most commonly used because they are easy to mount on posts and come in a variety of styles.

Post-tops lights are also another favorite for deck-lighting. They are decorative, easy to install, and provide subtle area light:

For your steps on the deck, you could consider recessed step lights or linear hardscapes under any step ledges: