So much of it depends on what I will photograph that day- Seniors, Weddings, Family Portraits, etc…
One area I will not waver on is the use of the best camera and lenses. The Canon L lens series do make a huge difference to image quality. There is no substitution. For example, there is about $1200 difference between the 50mm 1.2 and 1.8. While the extra light I can get from the 1.2 is amazing, it is the the sharpness, contrast, and saturation qualities the 1.2 delivers that is spectacular and noticeable.
How much do they each cost? An average L lens is $1500 in cost.
This is my gear for a Wedding:
Canon 5D Mark 3
Canon 5D Mark 2
50mm 1.2 L 600 Speedlight
85mm 1.4 L 2 580 speedlights
17-24 2.8 L Triggers-
24-70 2.8 L Pocketwizard Mini and Flex. I can fit it all into 1 bag!
70-200 2.8 mk2 L
100mm 2.8 L
My backups include the Canon 1D Mk4 and Canon 5D with Alien Bee strobes.