I usually shoot using only one sidearm and a rifle.
I've found that most of the rigs I end up using are military inspired rigs in black leather. Usually either one of four holsters,- a 'slim jim'; butt forward flapped-holster; or U.S. Navy pistol frog, all will hold either my Open Top or Leech & Rigdon cap'n'ball. The fourth is a field modified military holster for my '63 Remmington w/conversion cylinder which has the flap cut off and the holster wet-molded to hold the Remmie as if it is a strongside holster, even though it started out as a butt-forward flap. Gives it a slight forward cant that makes for a very easy draw.
Then I mix and match freely using plain belts,- two hook-and-eye adjustable with 2-piece buckle (U.S. Navy and C.S. Navy); one with oval "U.S." prong hook; and one with simple brass square buckle with tounge.
Ammunition is carried in a flapped cartridge box on the belt, either plain or U.S. Navy embossed.
I usually always carry strongside.
If for some reason I am shooting two revolvers then I carry either the 'slim jim' or the Navy frog on the belt as a crossdraw and the others strongside.
This has been a very flexible system for me and I've found I can cover quite a timeframe span.
RCJ