If you are referring to the feast for Obierika's daughter in Chapter 12, then the answer is the first wife brought coco-yams, a cake of salt, and smoked fish and the third wife brought a basket of plantains, coco-yams, and a small pot of palm-oil.  The celebration was one that would include the entire village, so members of the village would help provide food for the celebration and for the young couple.  Instead of valuable wedding gifts, like what we give today, these tribe members would provide valuable food items which were actually used as currency in their culture.

What did Okonkwo's first and third wives contribute to the betrothal feast?

In chapter 12, Achebe provides further insight into the important Igbo tribal customs by illustrating the uri ceremony, which is a phase in the marriage ritual that takes place after the bride-price has been paid.

In the uri ceremony, the suitor brings palm-wine to the bride's family and the rest of his kinsmen. The next day—after Okonkwo and Ekwefi's sleepless night with Ezinma—Okonkwo's family attends Obierika's daughter's uri ceremony. The ceremony is considered a women's tradition, and the women of the village gather at Obierika's compound to help his wife prepare for the massive feast. Achebe writes that Nwoye’s mother carried a basket of cocoyams, a cake of salt, and smoked fish for Obierika’s wife. Okonkwo's youngest wife, Ojiugo, carried a basket of plantains, cocoyams, and a small pot of palm-oil, while her children carried water to Obierika's compound for the feast.