I think speed is the key to a CSA victory. I build up forces as quickly in as possible in the east while causing enough havoc west to make the USA player think I'm going to go on offensive. The real plan, though, is to make the USA player build up forces and then slowly retreat, trading territory for time, and killing lots of USA troops.
Meanwhile, take Fort Monroe quickly if you can, definitely threaten it, but take Harpers Ferry as quickly as possible. Also take and hold the territory between Harpers Ferry and Alexandria/Manassas. Put a depot on it so you can hold it through the winter and you have a solid line on the Potomac. From there, you have to out-maneuver your opponent into exposing corps, one at a time. Encircle DC and make your opponent fight his way out.
I like to expand my railroads as much as possible so I can maximize use of my limited manpower.
If you're going to win, it's going to be before the end of 1863. Disregard the trans-Mississippi, it's a waste of time. Sacrifice New Orleans. Slaughter the Union in Tennessee. Overwhelm them in the East. That's my formula.