Hi:
For our S-gauge modular layout we use 16 gage stranded wire for the buss. We get the best deal locally at the automotive stores, they sell it as "primary" wire. Lots of colors and you can get it in 100-foot spools.
For two wire connectors we use the flat trailer connectors, also at the automotive stores. These have a 20 gage wire attached to them as opposed to the R-Shack version with a 22 gage wire.
We also use a lot of crimp connectors. They work well and go together quickly.
The above runs into some money if you do it for all your stuff, especially if you use barrier strips for handling multi-connection points. But all of this allows us the ability to change our layout and scenery, with a bunch of operating accessories, at every show.
$0.02
Ted