In the first book of the Old Testament, in Genesis 14, we see Abraham giving a 1/10 (tithe) of his possessions to a priest/king who is a type of Christ. This occurs about 500 years before Moses and the Law.
In the last book of the Old Testament, in Malachi 3, we read of God reprimanding the people for stealing from Him. When they ask how they have stolen from God, He replies, “In your tithes and offerings.” They have been withholding them. Then He commands them to bring their “full tithe” to the storehouse (treasury in the Temple).
Then God makes an amazing statement. “Put me to the test and see if I will not open the windows of heaven for you and pour down a blessing until there is no more need.” I can testify to this. Since my first job out of college I have brought my tithes to the Lord and He has always provided for me. Rather than me giving 10% to God, I consider that it is all His anyway and He generously gives me 90%.
The tithe is the minimal standard in Scripture because it also speaks of offerings. How I practice this is that I believe my tithe belongs to St. Patrick’s. Offerings go to other concerns that God has placed on my heart such as Nashville Rescue Mission, Food for the Poor and World Vision. However you choose to do it, I encourage you to make it a practice of giving to God first and not giving Him your leftovers. If we cannot trust the Lord to care for us materially why would we trust Him with our immortal souls?