I'll quote a past post of mine on this topic:
God's instructions on giving as Christians are as follows:
6Remember this: Whoever sows sparingly will also reap sparingly, and whoever sows generously will also reap generously. 7Each man should give what he has decided in his heart to give, not reluctantly or under compulsion, for God loves a cheerful giver. 8And God is able to make all grace abound to you, so that in all things at all times, having all that you need, you will abound in every good work.
2 Cor 9:6-8
You'll notice that there's no specific amount given. In the Old Testament, the Israelites were expected to give 10% of their income to the temple, so that's considered a good amount to give if you're not sure how much. Feel free to give more, though.
Here is my family's story about tithing. When I was very young, my parents were pretty poor. At that point, they were tithing out of their net income (money after taxes, SS, etc.) And we were living hand-to-mouth. Then, they decided to tithe out of their gross income (money before taxes, SS, etc.) After doing this for a little over a year (and God did provide for us that year), my father's job arranged to send him all around the country, and they paid for me and my mother to go also. They paid for transportation, and also for housing every place that we went to for about 18 months. It was absolutely wonderful, because they didn't have to worry about rent for that entire time. By the time we got back to the DC area, they had saved up enough to buy a house and send me to a private Christian school. Now, we still weren't millionaires or anything, but God provided for our needs.
Some other good verses about giving:
Luke 6:38 38Give, and it will be given to you. A good measure, pressed down, shaken together and running over, will be poured into your lap. For with the measure you use, it will be measured to you."
Malachi 3:8-10 "Will a man rob God? Yet you rob me.
"But you ask, 'How do we rob you?'
"In tithes and offerings. 9 You are under a curse-the whole nation of you-because you are robbing me. 10 Bring the whole tithe into the storehouse, that there may be food in my house. Test me in this," says the LORD A lmighty, "and see if I will not throw open the floodgates of heaven and pour out so much blessing that you will not have room enough for it.
The Bible says a lot more stuff about giving and about money in general. (Something like 400 references, IIRC, and that may just be the New Testament.) You could probably look it up in a concordance (if you have one) or find a devotional about it somewhere.
