10to1
Your paint musn't have good "hiding power" or else may have been thinned too much. On new work I think 3 coats are minumum for a good level of finish. White and off white have poor hiding power anyway because of the lack of pigment. Don't water the paint down too much and when rolling try and roll in two different directions, ie roll in the opposite direction for the subsequent coat. If you are on a budget you can buy large drums of white and mix in a small bit of coloured emulsion yourself, mixing up with a paddle attached to a power drill to ensure a good mix to give you an off white tint.