What effects do changes in the amount of gas and in the volume of the container have on gas pressure?
Volume is inversely proportional to pressure.
If the amount of gas in a container remains the same then according to Bolye's Law, increasing the size of the container (volume) will reduce the pressure. On a particle level this makes sense as the number of particles in the container doesn't change but the space they have to bounce around increase, which causes fewer collisions with the container.
By increasing the number of particles in the container you are going to increase the pressure. This is covered in the Ideal Gas law but it is also common sense. You are packing more particles into a container of constant size you are going to increase the interactions between the particles and the container.
If you are asking about what effect changing both the number of moles and the volume with have it would be entirely dependent on how much you changed each of them.