I have very little money and this is an rare opportunity to spend it on much needed personal items. Or should I spend my money on a poor person, giving them all of it. Or should I pay my sister all of it because I owe her a quite a bit of money.
"Let him who stole steal no longer, but rather let him labor, working with his hands what is good, that he may have something to give him who has need" (Ephesians 4:28).
"And let us not grow weary while doing good, for in due season we shall reap if we do not lose heart. Therefore, as we have opportunity, let us do good to all, especially to those who are of the household of faith" (Galatians 6:9-10).
Christians do what they can with the limited resources that they have. We cannot wipe out poverty. There will always be poor people in the world (Mark 14:7). You've nothing in regards to poverty if you make yourself poor by helping someone else who is poor. The goal is to work a bit more so that from your excess you can help those who cannot make it.
Helping the poor is just one of several responsibilities of a Christian. Those duties have to sorted by priority. First, a person has to work to care for himself. "For even when we were with you, we commanded you this: If anyone will not work, neither shall he eat" (II Thessalonians 3:10). This doesn't mean we aim for living in luxury, but we do need at a minimum be able to support ourselves before we can help others. "But if anyone does not provide for his own, and especially for those of his household, he has denied the faith and is worse than an unbeliever" (I Timothy 5:8). When you have family dependents, it is your responsibility to care for them. You don't give away money that your family needs to live on.
When you borrow money from others, you have an obligation to repay what you owe. "The wicked borrows and does not repay, but the righteous shows mercy and gives" (Psalms 37:21). Paying what you owe is a part of keeping your word. "But let your 'Yes' be 'Yes,' and your 'No,' 'No.' For whatever is more than these is from the evil one" (Matthew 5:37). First get yourself in a good financial situation so that you can give with causing yourself or others hardship, then you can generously give to others without qualms. "Therefore I thought it necessary to exhort the brethren to go to you ahead of time, and prepare your generous gift beforehand, which you had previously promised, that it may be ready as a matter of generosity and not as a grudging obligation. But this I say: He who sows sparingly will also reap sparingly, and he who sows bountifully will also reap bountifully. So let each one give as he purposes in his heart, not grudgingly or of necessity; for God loves a cheerful giver" (II Corinthians 9: 5-7).
As Paul pointed out in Galatians 6:9-10, when our resources are limited and the choice must be between help and fellow Christian and someone of the world, the Christian comes first because we are spiritually related.
"And just as you want men to do to you, you also do to them likewise. But if you love those who love you, what credit is that to you? For even sinners love those who love them. And if you do good to those who do good to you, what credit is that to you? For even sinners do the same. And if you lend to those from whom you hope to receive back, what credit is that to you? For even sinners lend to sinners to receive as much back. But love your enemies, do good, and lend, hoping for nothing in return; and your reward will be great, and you will be sons of the Most High. For He is kind to the unthankful and evil. Therefore be merciful, just as your Father also is merciful" (Luke 6:31-36).