The primary purpose of collecting the tithes and the yield upon it is to bless and benefit the lives of those in need. Assist the poor directly, looking for God’s guidance in so doing. Help provide for those who need housing, food, clothing, healthcare, education, and transportation, or children that need care. Take the money the Lord intended for the poor and administer it for the poor. The Lord desires us to have no poor among us.

One tenth of your surplus after you have taken care of all your responsibilities, all your needs, whatever’s left over — one tenth of that is your tithe. After you gather your tithe, look at your brothers and your sisters who are there in your meeting, and help those who have needs. Christians should take care of the poor among them, and no one should be looking at the flock and saying, I need your money to support myself.

The relief of the poor among you refers to the poor among the individual fellowship. If there are no poor among you, then excess donations should go to the temple, but they can be shared as your fellowship determines by common consent.  
Source: A Statement of Principles T&C 175: 42-44

Tithing is an offering to the Lord; one tenth of one’s surplus after all responsibilities and needs have been taken care of. The primary purpose of collecting the tithes and the yield upon it is to bless and benefit the lives of those in need. 

Tithing was never to establish a wealthy general fund nor to invite the wrongful accumulation of wealth that has resulted from the long abuse of this law. The law was to be a light thing, easily borne by the faithful. Tithing was always to be taken from surplus (meaning unnecessary excess property) and increase (meaning what remains after all costs of the household have been paid). It was to be drawn out of the abundance in the possession of the giver so that there may be enough and to spare, not from property required for their necessities. The tithes of this people are to be used for the poor among this people, if they want to become Mine.
Source: T&C 173

“Assist the poor directly, looking for God’s guidance in so doing. Have no poor among us. Help provide for those who need housing, food, clothing, healthcare, education, and transportation. Take the money the Lord intended for the poor, and administer it for the poor.”
Source: Preserving the Restoration, 256, 258-259