To add onto Rich's advice, I'd take some of the gravel and put it in a new filter bag (or in my case the foot of pantyhose). Then put this in your filter. This will give you the most contact time with the water and the bacteria on the gravel, and should seed faster on the filter. I have an aquaclear filter that has room for 3 inserts (suggested to use foam filter, biomax beads, and charcoal).
What I did to set up my 20gallon was to put the foam filter on the bottom (first filter step to get rid of large waste and such), then put the seed gravel in the pantyhose next, and then the biomax beads last. My reasoning was that when the bacteria would spread from the seed material, it would adhere to the biomax beads and spread from there first. While you want the bacteria all over the tank (plants, substrate, glass), the bacteria that do the most work getting rid of ammonia/nitrIte are found in the filter since it gets the most constant flow of tank water.
With this "seed" filter insert, and another small bag of gravel that I kept in the tank and every day or two squished it around to get some of the bacteria on the gravel to dislodge and hopefully coat the tank and filter elements, I was able to fishless cycle my new tank in about 2 1/2 weeks from start to addition of fish.