From "Cowboys & The Trappings of the Old West" by William Manns and Elizabeth Clair Flood.
This Texas Ranger of 1887 posed with his horse. I don't think too many people would call this big horse a pony. Note the Winchester '73 on the saddle holster, left sie, the rope, the bedroll. The Ranger is wearing what appears to be a Stetson "Boss of the Plains" hat or a copy. It was a very popular style. It's hard to tell, because the photographer, like all good photographer, said "put your hat back on your head so we can see your face." Now we know what the ranger's face looked like, but not what the hat looked like on top. Considering that some Rangers worked in south Texas and picked up sombreros, it could be a sombrero.
His shirt has a collar. Not all of them did. He is wearing a tie. The shirt is striped. He is wearing gloves and carrying a quirt. He is not wearing suspenders, but, of course, he is not wearing a belt for his pants. The belt loop had not been invented by then.
On the gunbelt is the ever present Bowie knife. He is wearing his holster cross draw. It isn't a cross draw holster, rather a straight drop holster worn on his left side. This puts the cartridges in front. The pistol is the everpresent Colt, probably .45 Colt caliber, with ivory grips, and it is nickeled. Most rangers wore blue guns, but enough wore nickeled ones that one could be authentic with either.
In 1874, when James B. Gillett joined the Texas Rangers, he had a Colt .45 with a 7-1/2" barrel. The gun had been introduced in that configuration only and was quite rare at that time. Eventually the Colt 1873 SAA revolver became pretty standard among the rangers. In 1875 the shorter 5-1/2" barrel was introduced. Then in 1878 the 4-3/4" barrel was introduced. In 1879 the .44WCF or .44-40 cartridge was introduced in the "Colt Frontier Six-Shooter." The advantage of this was the Winchester '73 was chambered in this powerful cartridge. Then a cowboy or a ranger could carry one cartridge belt instead of two, and one supply of ammunition instead of two. In a fight, putting a .44-40 cartridge in a .45 Colt chamber could be quite dangerous.
The long-barrelled Colt pretty much demanded a cross-draw holster when worn riding a horse. The advantage of the shorter barrels in handling also extended to their being viable in strong-side carry. Rangers carried one six-shooter. The two-gun gunfighter was mostly a Hollyweird myth, but they did exist. The primary weapon was the Winchester '73. See the page on James B. Gillett.
His boots are square toes with a molded one-piece front, and he has on spurs with large straps and some drop to them.