No single musician has been more important to the creation and development of jazz music as Louis Armstrong. In fact, this web-site is dedicated to musicians who were either directly or indirectly influenced by Armstrong. Modern players– even those that may not often listen to Louis Armstrong, may still be indirectly influenced by Louis. It is as Miles Davis proclaimed: ”You can’t play anything on a horn that Louis hasn’t already played.”
There is a vast ocean of recorded Louis Armstrong music; I suggest that you wade into a boxed set or collection first to get an idea of the style and variety of music he performed throughout his over-50-year career. For the earlier part of his career, I recommend the Hot Fives and Sevens box set (mp3 version here). For a general overview of his later career, I recommend Verve’s Jazz Masters 1: Louis Armstrong.