This topic's been extensively covered here and on the 'Historical Society Forum'.
Page through the back postings of both forums, and you should find what you want.
You're right in thinking that they didn't use uniforms - as contract employees, they didn't.
The 'actual' Indian Scout did, though - and that's been addressed as well.
Your style of dress would be that of the common working man of the time, and your weapons wouldn't be issued, since you'd've been expected to supply your own.
You could perhaps purchase a canteen and poncho/rubber blanket in town - sold by a deserting soldier as he headed to the gold fields - but the Army really wasn't going to provide very much.
Good Luck.
Scouts Out!
If you are referring to Indians hired as scouts, then articles of uniforms and weapons
were usually issued. These were not generally new clothing or guns, but that varied. Usually, they were issued sack coats, especially if attached to cavalry units. Also these scouts often wore articles of clothing of their own, such as breech clouts, leggings, moccasins, etc. Weapons varied. After about 1874, they might be issued obsolescent, limited standard .50-70's, while the regular troops had .45-70 Trapdoor Springfields. On the other hand, if those secondary weapons weren't available, they might, indeed, be issued .45-70's. In the Big Horn and Yellowstone Expedition of 1876, some of the Indians WITH Gen. Crook's column had Spencer carbines, and some had M1873 Trapdoor Carbines.
"White" civilian scouts were employees of the Quartermaster Dept., and were paid pretty well, depending on their skills, experience and useage. Buffalo Bill Cody was paid $150 per month! Others were paid only $30 per month, plus one meal a day. If scouts were furnished horses then they were not reimbursed. OTOH, if they supplied their own horses, they were paid for the use (not sure of the amount).
As to weapons, civilian QM employees might be issued arms as appropriate to their duties. Frank Grouard, Crook's chief scout on the Expedition, for example, was issued one Colt's revolver, cal. .45 (presumably a Single Action Army), for which Maj. Coates was responsible, but also bought, from Army stores, another Colt's. The cost of the gun he bought was deducted from his pay.
Likewise, other QM employees might be issued (loaned) rifles, carbines, pistols, etc., depending on their duties. A teamster, for example, who was with the troops in the field, was usually issued a rifle or carbine, depending on the unit to which he was attached. If obsolescent guns and ammo (ammo was usually available by the thousands, even after the changeover to the .45-70 Gov't small arms) were issued, the were usually out of the Ordnance stores of that unit. In some instances, a few .50-70 carbines were retained at each post just for that purpose.
These civilian employees sometimes turned in the guns when they terminated employment. A few times, they acquired the guns. Now this was NOT strictly legal under regulations, but that was usually gotten around by "losing" the item in question, and having the cost deducted from their final paycheck or paid by cash...if they had any left after visiting the suttler's store.
There are several notations in the records of a rifle or carbine and an even 100 rds of ammo being "lost" and the value deducted from the pay.
Hope this is of some help!