Stop in for a cup of coffee

But follow the wires from the alternator output to the battery positive.
They both end up at the same place. The Main junction - usually a welded splice.

So for the subsytems you can start tracing from the main junction.
Several important systems never go through the fusebox.
A few circuits go through fuse box but not the start switch,
That's why starting at the fuse box could get confusing.