拋磚引玉

Etymology
One of the , originally in reference to tossing brickbats at one's enemy to get an (exploitable) reaction or win a greater prize.

Idiom

 * 1)  to offer one's own relatively worthless words, opinions, or services in order to attract others' more valuable contributions
 * 2)  to achieve success by goading one's opponent
 * 1)  to achieve success by goading one's opponent