All this has been very useful. Thank you, folks.
Going to the "what", and taking @Phil Starr's advice
Lighting to make the band look good - yes.
Lighting to allow the band to see what they are doing - yes, definitely.
Lighting to improve the audience experience - yes.
Plus
Ease of use for total noewbie.
Ease of set-up.
Expandable for the future.
Easily transportable.
The band I've just come out of had a t-bar with, I think, 6 PARs and they pointed in different directions, some flashing colour to sound changes, others just lighting the band. It’s amazing how little notice I took and now with the new band, I need to know all about it.
Here's a link to some video from Saturday night. It's a very typical venue layout, the stage area was generous for a 4-piece.
How would you go about lighting that if it was your band?