Season 1 of Babylon 5 is an excellent starting point for the series. The season introduces the characters, the locations and the races used in the next four seasons.
When viewed independently, the season can seem a bit weak, but when viewed with the other seasons, it becomes apparent just how much is built on what happens in this one.
Would definitely recommend as a great example of science fiction, and even after nearly 20 years, it still stands up as an excellent show in it's own right.