in your example, yesSo, (for example) if it takes 4 drops of ammonia to reach 4-5ppms. and one day the ammonia is 2 ppms. Then you just add the ammonia one drop at a time and test it after each drop until it reaches 4-5ppms.?
Also, would it be a good idea to ask the pet store if they will give me a little scoop of their aquarium gravel to get my bacteria started? or would that be a bad idea?
As waterdrop said it is a good place to get diseases. I don't like doing it for several reasons. Disease and the gravel has little beneficial bacteria in it compared to filter sponges, unless the gravel comes from a well maintained undergravel filter.
Just let the tank cycle naturally and you will have a healthier tank to start with.