Aruch HaShulchan, Laws of Tzedakah 251:5

Therefore, in my humble opinion it seems clear that Rav Saadia Gaon’s words [that one’s own livelihood precedes one’s need to support others] are regarding one who does not have more than a little bread and water. Accordingly, the Gaon brought proof from the Tzarfatit widow, where actual lives were at stake because there was a famine in the world, as we see in the Book of Kings I (17:12). And if there remains extra bread and water, one’s parents get precedence, and then the children. But regarding one who has a large livelihood, like a distinguished member of the community who has sufficient bread, meat, spices, and clothing, and dresses like a wealthy person, this person is definitely obligated to give a tenth or a fifth of their earnings to tzedakah. A large portion of the tzedakah that you give should go to your relatives and the poor of your town. You are also obligated to give a little also to those who live far away, and to the poor of another city. Because if you do not, a city of poor people will diminish in a famine, God forbid. And know that the reason we have these rules in place is because if we didn’t, there would be no limit to the individual’s wealth that precedes [charitable giving], and everyone would say “I need my livelihood, all that I can amass, because there is no limit to what I can keep [for myself].” Therefore, we do exactly as we said before - [the laws of preserving your own livelihood before supporting others] only apply to one who has a little bread to satisfy themselves and their spouse and children. [Translation by AJWS]