Paul stresses the abundant nature of God's giving toward us so that we may give abundantly in response. 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. The Old Testament commanded a tithe (10% of income). The New Testament is far more radical - we are to be generous givers of all we have. Some will give far more than 10% of their income, others less.
Each person should give what they have decided in their heart to give. We need to think carefully about what resources we have been given, what our responsibilities are and how we can give money in the most effective way.
God loves a cheerful giver. It's easy to give for the wrong reasons - to relieve our guilt, to avoid other avenues of Christian service, to be seen to be generous by others. Paul tells us that God loves a joyful and big-hearted response to all that He has lavished on us.