Recommendation #1 would be a power feed for every 6 track joints. Just a SWAG, but maybe as many as dozen feeders.
If you're running command control only (including LionChief) a MTH Z1000 brick should be more than adequate. Another inexpensive option would be a Lionel P-135 (6-12866). For running conventional, a MRC Pure Power AH501 would be a decent choice.
What transformer do you have now? The newest come with a wall wart. The oldest came with an early CW80. I honestly cannot recall a PE set that came with what I would regard as a "good" transformer.
