All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The husband is obliged to be just between his wives with regard to staying overnight with them, spending on them, clothing them, and providing housing for them. For more benefit on this, please refer to Fatwa 82124.
As regards the dowry, according to the most correct opinion, it should be agreed upon and defined by the husband and wife; please refer to Fatwa 90124 for more benefit. There is no difference in this between the first wife and other wives, and the husband is not obliged to buy the same quantity of gold and other things that he bought one of his other wives, but it is desirable for him not to prefer one of his wives when gifting them over others, as this affects them and it might even lead to spoiling the harmony in the family. Allaah Knows best.