Actually, there should not be a set limit as to what you contribute to your church of choice. What matters is that you do what you can, cheerfully. 2 Corinthians 9:7 (NIV) says "Each of you should give what you have decided in your heart to give, not reluctantly or under compulsion, for God loves a cheerful giver." The best you can give your heavenly Father is your time and wholehearted effort to live your life according to his principles and by telling others of his wonderful works and purpose, as found in the Bible.
Christians are not under the Law Covenant given to the nation of Israel. For when Christ came, the law ended. (Compare Galatians 3:19-24) So they are not require to give a certain amount to God. In the bible book of Luke chapter 21 verses 1-4, Jesus "saw a certain needy widow drop two small coins of very little value" into the temple treasury chest . How much did her donations amount to? Only 1/64 of a day's wages. Yet Jesus said that this small sum was acceptable. In the bible the number 10 represent completeness. So any donations that a person make should be whole-souled , for God is looking at the Quality of one's service to him and not the Quantity. ( Read also 2 Corinthians 8:12 and 9:7). I hope and pray this answered your question.
Find a church (your home church preferably) or other Christian organization and give at least ten percent. I give to my church, KLOVE/Air1(non-profit christian radio), and sponsor a child thru World Vision (Christian based, 86% of all donations go to the children and their support, only 14% goes to admin and fund raising, etc.) Start by placing money in the offering plate or basket at church. Call your church office and ask how to make official donations. Look into other worthy christian charities.
Good scripture for tithing is Malichi 3:10.this saysGod says: "test Me". But i love: Luke 6:37-38 Believe me: the more you give from your heart)- the more you get back( blessings dont always come in the form of money!) some say: the OT doesnt apply. i say test Him and see that the Lord keeps His Promise. and DONt give Him your leftovers(crumbs). he will supply all your needs according to His riches in Glory!( He doesnt Need anything we have-He wants you to help others in His Name!