If you have a lower/mid–price guitar, you can improve things by replacing the standard wiring and potentiometers. Of key interest is the pots’ resistance value because the cheaper they are, the more they tend to vary.
A Strat, for example, can sound very different with 300k or 200k pots (the ‘correct’ value is 250k). Likewise, 300k and 500k pots – both common fitments – sound quite different in a Les Paul or ES-335.
If you’re replacing low/mid-range pickups, we’d do this as a matter of course. The wire gauge isn’t really important over short wiring runs like this, but for reference, Gibson and Fender’s vintage spec favours 22-gauge, tinned, stranded wire.