R2thaSAR, what price have you found for Eco-Complete? I recently ordered some -- wasn't too expensive, but the shiupping can get you.
2 bags should be enough. It doesn't have to go under your gravel and can be mixed into existing gravel, but under is recommended (if you are setting up a new tank).
Also, as you eventually find that your plants are not getting the nourishment they want, you can use Jobe's Plant Food Sticks, but make sure you get the specific type for "lush plants and ferns," with the numbers "16-2-6." Some people break the sticks into halves or thirds and stick them into the substrate.
By the way, if adding 2 bags of Eco-Complete to your gravel means you will have a substrate of 3" or maybe as much as 4" should be okay, especially if you buy plants that are pre-rooted in planting "blocks" and you want to plant them (with the blocks) into your substrate.
Don't get the regular Jobe's houseplant sticks.
Speaking of which, does anyone know where I can order the Jobe's "fern" sticks online? Please let me know.
Thanks in advance,