Been thinking of doing the big 3 wiring upgrade but not really sure where to start. i have a 94 st203 but doubt it is very different on others

has anybody here done it and could guide me through or give me tips?

have a 2400w sound system and getting sick of the surges

I have upgraded only my positive wire running from the alternator to the battery.
Battery to chassis and engine to chassis seemed efficient enough for their length.
You basically buy a wire, put terminals on it and link the desired places.

Here is a pic to help you choose what thickness wire you should get considering the amps that will run through it and it's length.