"Giving" can mean many things. And God gives many kinds of blessings.
In the Old Testament, God instructed the Israelites to give a tenth of their produce and livestock to the Lord (Leviticus 27:30-33). There were also admonitions to be generous (such as Proverbs 11:24, 25), and promises that "he who is generous will be blessed, For he gives some of his food to the poor." (Proverbs 22:9; also see 19:17)
Many Christians quote the statement of the Lord: "Give, and it will be given to you. They will pour into your lap a good measure–pressed down, shaken together, and running over. For by your standard of measure it will be measured to you in return." (Luke 6:38) Some believe this refers to financial donations. In the New Testament we find no instructions to tithe nor to give financially, except to those in need (Acts 11:29-30, 1 Corinthians16:1; 2 Corinthians 9:12). We know that St. Paul and those ministering with him did not depend on monetary donations from the congregations they served (Acts 20:33,34; 2 Thessalonians 3:8). The Lord does not expect His followers' greatest gifts to be financial, nor are they to expect financial blessings in return.
In Luke 6 (above) the Lord is teaching His followers that they will have to face opposition in this world, and He warns against having riches. His great lesson in regard to receiving a "return" is how we must be generous in spirit towards others, even our enemies. He wants us to do good and have mercy (verses 27-38). This is the kind of giving He expects most from us. And then he will bless us with His love, mercy, strength, and wisdom in our lives.
Our Heavenly Father "knows what you need before you ask Him" (Matthew 6:8). He promises if we seek first His Kingdom, "all these things" will be given us. (Matthew 6:33) Therefore we trust that the Lord will provide for all we need, according to His wisdom.
Our Lord knows that being generous will build our character, make us happier, and prepare us for a place in His Kingdom. The Apostle tells us: "Therefore I urge you, brethren, by the mercies of God, to present your bodies a living and holy sacrifice…" (Romans 12:1) He wants every part of our life – our time, talents, and resources – in His service. But this should come from our love and joy in Him, not just because He commands us to.
When we realize that "He Himself is the propitiation (satisfaction) for our sins; and not for ours only, but also for those of the whole world" (I John 2:2), our hearts overflow with joy to know that there is hope for us and even for the whole world. Christ's love comes into our hearts, and we want to give as He gave.