ok :) for gravel based tanks I like to set up the tank first woth water. take your time deciding on where you want everything to go. it's much easier moving things around in gravel than in soil, that's for sure :)
you will want to plan out your tank so that the plants that grows taller (stem plants- are at the back. and the shorter ones at the front. best also, if the tallest plants are on the side with the small plants towards the center :)
play with the composition. if you have the resources, a large rock or drift wood can really bring the tank together.