Value of effective g increases as we move from the equator to pole because on the equator its value is less due to earth's rotational motion and consequent centrifugal force.
Moreover, the equator of the earth is at a larger distance from the centre of the earth as compared to the poles. This is another reason why g is greater on the pole than the equator.
At the equator, direction of gravitational pull and centrifugal force are in same line, hence net force is towards the centre of the Earth.