For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Seems to me the first decision is: do I live under the Old Covenant (and therefore am judged under it), or do I live under the New Covenant (and am judged under it)?
The best way to figure out what you're spending — and what can be cut — is tracking every last item you buy - an app like Geltbox money will help you keep track.
The bible does say pay your tything and you will blessed accordingly
Tithing was a requirement of the law and since the church is not under the law means believers are not under compulsion (or law) to tithe. The New Testament teaches that believers are to be cheerful givers (2 Corinthians 9:7) and our gifts should be "in keeping with your income" (1 Corinthians 16:2 NIV).
All of this talk about spending should awaken us.
Giving to a ministry from the money a person earns at a job was never a custom of any people of the bible. Tithing was a way of supplying for the needs of the Levites, whom were the temple workers. They couldn't work at the temple and farm a piece of land at the same time. So they were taken care of by everyone else, whom were given the Levite's share of the land when the land was distributed.
I've never farmed or raised any sheep or any of what they sacrificed and gave.
The ministry, the house of worship we support have needs. The workers need to be cared for. The apostle Paul told the early church how to care for the needs of the church. He said to give as you have prospered, and to give cheerfully, because "God loves a cheerful giver." He never told the church to tithe of the money they made working at Wal-Mart. He never mentioned tithing at all as a custom the church would be governed by. But I think it's a good way to determine what to offer. Like I said in my answer: if you give from feeling compelled you should keep it. God's work can get done without that kind of sacrifice. He owns it all and has sovereign power and control. He'll take care of His church. He'll also take care of the person who feel they can't afford to give a 10% offering. If you think you can't afford it you probably can't. Keep it and don't worry about it. Give what you can. Feel good about giving. LISTEN AGAIN: GOD LOVES A CHEERFUL GIVER. Do that.