Mike,
Which branch? Infantry cavalry artillery? Also you may check with the command structure of the group. Some can get real picky as to there idea of a uniform. Even giving you a list of approved venders, and you can only buy from these people! Some units are more relaxed though.
The basic uniform for any branch is a pair of sky blue trousers, a 4 button dark blue sack coat, a shirt, and pair of brogans, aka Jefferson bootees. Also a waist belt with oval US buckle. Top top it off a hat of some kind. Again this can be tricky. A forage cap is usually universally accepted, a kepi depending on unit, or a black "slouch hat" is sometimes accepted.
Books I would recomend would be Lord's encyclopedia by Francis Lord. I believe there are a total of five volumes. Has pictures of original items plus brief descriptions of said items. Another Is a series put out by Time Life called "Echoes of Glory" There is a Union and Confederate edition. These are mainly pictorial, but really cool! Check out your local library they can probably get them for you through the loan system if they do not have them.
I am a retired soldier as you might assume. It has been a few years, but I would be more than happy to help. Any more questions please feel free to ask. You can pm me as well!
PS I have two checked CW era shirts I would sell cheap, or trade for late 18th century early 19th century items.