The Bible says that we should give 10% of the gifts that God has given us back to God -- well actually to the church for its outreach ministries especially and to cover other monetary obligations (rent, utilities, taxes, etc). In a modern world, this means 10% of our income. In other words, we must return a dime for every dollar, a dollar for every ten, ten for every hundred, a hundred for every thousand. Well you get the idea.
Said the latter, each of my boys should give a dime for every dollar I give them for sweets or such goodies. Honestly I don't think they would be thrilled by the idea.
The problem is what to do when one's money is spent in personal debts, medical expenses and such (90 to 95%). Can a person do both -- tithe and take care of himself and family while living paycheck to paycheck?
Most people in this latter scenario would cover his own expenses especially when dealing with family and/or medical expenses. Why do I bring this up? I don't have enough money (sometimes any left over) to tithe after expenses on my children and medical expenses, neither of which is optional. I merely give what I can -- a set dollar amount every week. Yet I know this isn't enough, never enough.