Is the husband sinful for putting most of his money into his first wife's house and allocating only enough for monthly expenses to his second wife?

As long as the husband spends on his wife in a reasonable manner, there is no sin upon him for what he spends on his other wife and the gifts he specifically gives her. He is not obligated to equalize between his wives in spending and clothing if he fulfills the obligation for each one of them. He may prefer one over the other in spending, desires, and clothing, provided the other wife has sufficient provision.