Make sure the hardware is iron, not brass. Felt hats can be purchased at many department stores in the fall. By adding a silk hatband and dark trim tape to the brim, and a little reshaping, you can make a decent slouch hat that will be less expensive than a sutler usually will be. You can get by with one pistol and a saber for a while. Though the original 7 th Cavalry used mostly Colts, a Model 1858 Remington is sturdier.
Extra cylinders are easy to replace on horseback and cheaper than buying another pistol.
Consider Brogans for footwear as they are half the price of a decent pair of boots. Buy the best canteen you can afford. A wool covered stainless steel one will give you good service and won't rust. A list of reputable suppliers is at the bottom of the Membership Requirements page.