Battleshirts were very common. Usually grey or light colored wool, trimmed with military trims in black, red, blue (trims from officer leg stripes, mounted jackets, officer kepis, etc..)

Required: Period shirt or variation of a battle shirt

Required: most any color jean wool trowsers

Required: captured federal smoothside canteen

braces (suspenders) made of canvas or leather, stay away from elastic

slouch, derby, or beehive hats are far more common in the west

black brogans - the old standby

homespun haversack or tarred yankee haversack

forked and frame buckles were common.

Option: grey sack coat. for some Southwest battles, even federal sack coats were worn

Option: Shield shirts were popular in the early war. A good option for hot weather too

Option: civilian clothes and vests were very common in lieu of uniforms

Option: CS buckles were not common in the west (like uniforms). Texas state buckles were also somewhat rare

Option: Standard Infantry or mounted Sky-blue trowsers

Option: stovepipe boots were very popular with Texans

Option: gray kepi is not nearly as common as slouch hat

Block I or Federal eagle buttons were the most prevalent. But Texas state buttons are acceptable, just less common (like uniforms)

Option: wood canteens were early war, but trans-mississippi areas were not well equipped.