In addition to the tutorial, I attempted to play the Gettysburg scenario last night as the CIA and got hammered. I was tempted when I saw Baltimore looking undefended and ready to be plucked to meet the NM condition for a CSA victory. But my mistake was sending Ewell to grab it and not joining the ANV together to do it. (Well, succumbing to the temptation was my mistake, but you get the idea.) Lee was sitting in Gettysburg in a defensive posture and got clobbered by Meade repeatedly. I would have used Ewell there.
This is a very simple scenario, so it is better to consilidate in Gettysburg and wait for Meade to attack you while you're concentrated? What if you do that and Meade never moves?