God is generous and so he calls us to be as well. What we do with what God has given us shows the world where our hearts are at and helps proclaim the gospel. We want to glorify God with every area of our lives, and that includes what we do with our finances.
Giving of our monies ("tithes and offerings") is not about earning favor with God. You cannot earn His grace. It is freely given to us. We give back to God what He has entrusted to us already. Thus, giving money is a form of worship. However, whenever, and whatever you choose to give to God, do so in a worshipful way. May this be worship to God for you!