22AWG stranded wire for supplying power and ground to the Wii, 26AWG wire for powering smaller peripheral components like the screen, and 34AWG or 38AWG enamelled magnet wire for data lines and small relocations. For the stranded wire you want at least 2 colours of each gauge, red for positive voltage and black for ground. It's also recommended to have 4 additional colours so you can use one colour for each of the 5 voltages, and reserve black for ground. Having a second colour of magnet wire is also helpful to prevent confusion when doing the USB data lines and other small via connections. You can usually find magnet wire in orangey-red and greenish. It's also recommended to use silicone jacketed stranded wire if you can get it. It's more flexible and doesn't burn/melt or hold a memory as much as PVC jacketed wire.