Giving is an act of worship and obedience from a heart surrendered to Christ... a choice we make to follow God's instruction for us. We give out of our need to act on our faith. God uses those resources for His glory and to further His Kingdom.
God calls each of us to give 10% of our "first fruits" to the "storehouse"... to the church we've been called to serve. Tithes help us to create quality environment, ministries etc that we all enjoy. As Rhema Assembly, a body of believers, we've been called to tithe
Occasionally, God calls us to make sacrificial offerings above our tithe. There offerings are usually designated to a specific capital steward campaign, outreach etc. In addition, your obedient generosity also increases the faith of the recipient