Holding prejudice against a black/brown person is bad, holding prejudice against a fat/ugly dressed person is bad, holding prejudice against WOMEN is bad.
But some are more critical than others. A black person can be black, fat AND a woman. But, what affects most is the prejudice against race (because there isn't a system holding down the fat man the way it is a system holding down the black man).
So - i'd start with my prejudice based on nationality/ethnicity(sp)/race. Then it should also be easier to deal with the others.