I disagree with avidgamer slightly. The Confederates went to war wearing a lot of militia uniforms, thus all the kepis you see in photos. I wouldn't get too hung up on kepis vs forage caps for the CS, as there was more variation in construction than with Union bummers caps.
Anyway, after the first run of uniforms wore out, the Confederacy clothed their soldiers through the commutation system (basically reimbursement for private purchase). This is where you see the trend towards slouch hats as people had them sent from home. Good quality hats were in high demand, thus the the unadorned black 1858 "hardee" hat was a prized item to capture from the Yankees.
From late 1862 on, the Confederacy went to the depot system and actually massed produced and issued uniforms. Contrary to legend, the confederate armies were pretty well equipped into 1865, especially as they retreated onto their depots at Columbus and Atlanta GA, Charleston and Richmond. Sherman's army kept an inventory of what they captured in Columbia, SC in 1865 and there were literally thousands of brand new Enfield rifles, pairs of shoes, and kepis/forage caps.
But for wargaming purposes, the following is decent guidance:
More slouch hats in the west compared to the east.
More kepis/forage caps for 1861 and 1864, predominantly slouches for 1862, and a mix for 1863 and 65.
Just my 2,000,000 confederate dollars worth
Jeff