If you can only have 1 DVD from the first season, THIS IS IT! Don't let the low number of episodes on the disk fool you, this DVD is well worth buying. The 3 episodes are not only meant to be viewed in order but they are also carry a very intertwined and on going story line.
Episode #19, There But For The Grace of God, is about Daniel's trip to an alternate universe where he gets a glimpse of a possible future for his universe. It is helpful if you had seen the previous episode, Torment of Tantulus, but not required. Very action packed episode.
Episode #20, Politics, takes up literally where #19 leaves off, with the SG-1 team cleaning up from the previous mission. An evil budget cutting senator is out to get the Stargate program and the team must justify it's existance in a hearing. Ends as a To Be Continued.
Episode #21, Within the Serpent's Grasp, is the season finale and begins with the SG-1 team AWOL in an attempt to thwart the Goa'uld attack against Earth and justify the existance of the Stargate program. Another "To Be" episode that leaves you hanging and wanting more.