How money should be spent according to scriptures (sashtras)?

The sashtras enjoin that if one has money one should divide all that he has accumulated into five divisions–one part for religion, one part for reputation, one part for opulence, one part for sense gratification and one part to maintain the members of his family. At the present, however, because people are bereft of all knowledge, they spend all their money for the satisfaction of their family. Srila Rupa Gosvami taught us by his own example by using fifty percent of his accumulated wealth for Krishna, twenty-five percent for his own self, and twenty-five percent for the members of his family. One’s main purpose should be to advance in Krishna consciousness. This will include dharma, artha and kama. However, because one’s family members expect some profit, one should also satisfy them by giving them a portion of one’s accumulated wealth. This is a sashtric injunction.

Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Eighth Canto, Chapter 19 – Text 37