It is best not to use the same gauge (size) of wire for all your model railroad wiring. The higher the gauge numbers the smaller the wire e.g. a size 22 gauge wire is smaller than size 18 gauge wires. The larger size wires (e.g. gauge 18), are generally better for longer runs as it minimizes any power loss. Many use size 22 gauge wires for short runs (e.g. a 1-foot drop from the track rail to the bus wire). Sizes 22 – 25 are often used for lighting circuits, short runs, and for powering relays. If you keep the relays for your frog power reasonably handy to the turnouts they control, you can probably use size 22 to route the power to a frog from a bus or the track. DCC typically requires heavier bus wires to minimize loss.