Hi there! I'm Madrana and I'm a holy paladin who uses Grid regularly to help me heal.
As awesome as Grid is, it's not quite the most user-friendly add-on that you will ever use. It's not that things are difficult to set up, but you do need to know how to set things up to be sure that things actually show up the way you want them to.
To that end, here are some guides I've written to do with Grid. While most of this is from a healer's perspective, I know that some tinkering of Grid is extremely useful for raid leaders and I would highly encourage any raid leader to modify their Grid to view specific buffs and debuffs.
Wild Growth, Grid and Clique
How to Display Debuffs in Grid
How to Display Buffs in Grid - Part 1
How to Display Buffs in Grid - Part 2
Enjoy and happy healing. :)
(Feedback is welcome at madrana [at] apotheosis-now [dot] com!)