Well, I heartily recommend any Batgirl trades you can get your hands on, Steph or no. Batgirl: Silent Running is out of print, but the trades that are available are:
A Knight Alone Death Wish Fists of Fury Kicking Assassins Destructions Daughter.
Steph is present (and awesome) in the last four as a bonus! Also, Batgirl #38 is great Spoiler stuff and get Batgirl #53 for the Steph/Robin teamup (it's not in trade)
I wholeheartedly recommend the Robin/Spoiler Special. It's also available in the trade "Robin: Violent Tendencies" which chronicles Steph fantabulous return. Robin Adventures pre Willingham aren't collected in trade (except for Flying Solo, which has the first seven issues which include Steph's #3-5 appearance, but it's out of print. I'd suggest #3-5 if you can find the individual issues, as it's good early Steph.) Robin #100-105 is chalk full of Steph goodness, and her dad's death arc with is Robin #107-#115 is another personal favorite.
The trade "War Drums" chronicles Steph's time as Robin (except for Batgirl #53) The Robin 80 page giant and Huntress/Spoiler: Blunt Trauma are other decent Steph oneshots.
You can find all Steph's appearances in my handy dandy Steph Wiki "Appearances" section.
The Robin section is particularly handy, as it's by far the comic she appears the most in and can help you understand which issues to follow to get a character arc...for instance, the pregnancy arc is Robin #57-65. The "finds out Tim's secret ID" are the issues listed for #80-#99.