First off, welcome Kogre. You did good by reading up on here, but it sounds like you just need to spend some more time reading to see what fits you best.
Filter media won't really compete with your substrate. They will work together. You'll only have as much nitrifying bacteria as there is food (ammonia) in the system to feed it. Doing a fishless cycle with ammonia won't hurt your substrate.
Don't worry about carbon in your filter. It wears out in a matter of days anyway. Save it to use for removing traces of medication or to clear up cloudy water.