Two major factors when it comes to breeding mice is temps and nutrition. Temps need to be maintained from the low 70's to the mid 70's. Anything much above 75 will begin to have an adverse effect on reproduction. Also make sure that the mice are being fed a good quality diet. Mazuri is a good choice or any other comparable brand.
When I used to breed mice, I did a 1:5 ratio in a rack system. It is important not to move the males around much. Each male had his own tub and females were rotated into "his" tub until they became pregnant at which point they were moved to a nursing rack and a new female took her place in the breeding rack. Most mice don't really start breeding until they reach 8 weeks or older so if the mice you got were from a pet store, more than likely they were just past the hopper stage 3 1/2 to 4 weeks old. Be patient and give it some time. Once they do start breeding you will have more mice than you know what to do with.
Good luck!