Back to the Question.
When I buy ammo instead of reloading it, I will get the 100 Pak's at Wal Mart, either Federal or Remington. Shot size, either #7-1/2 or #8 shot will work fine. Normally the ones referenced above will be a 1-1/8 Oz loads.
I normally get the Remingtons, as my reloading components work in them, and I save my hulls.
Due to all this Hope and Change, shot has gotten so expensive that most of the guys are just buying bulk pak shotgun shells instead of reloading at the moment.