I think you should have filled your squad with bronzes and level all of them at least 20 to get them work for most things. I increased storage to 120, farmed every type of 2* girl and used 10 of them on the same type of 3* After that i used 5 1* and 5 3* manyus to get all of them straight to 30lwl, but its dependent on how much you farm manyus in one day.

A small tip: with a little calculating using 9 2* girls of same type and 1 2* another type makes a bronze girl 8lwl %95 which is a bit cheaper to level further than lwl 9 (which is achieved with using 10 2* same type) and at 8lwl %5 is nearly nothing