I'd add in the S2 finale "The Jem'hadar", as it does set up the S3 premiere.
suggested that the OP watches a select few from season 1 and then the entire season 2, which I agree with. (In addition the list, maybe the OP could also watch The Forsaken
from season 1 because Lwaxana comes back a few times in later seasons and her relationship with Odo builds on The Forsaken
Season 2 does have a few clunkers but so does season 3, and it's not bad overall as season 1. I'd list Melora
, Second Sight
as season 2 episodes that aren't essential in any way and can be skipped (though there are people who like Melora