We are all called to represent God in this world no matter who we are. Each one is given a specific assignment. One is not better or bigger than the other in the assignment given by God. But each of us do it differently.
The volume of what we do is immaterial. But the faithfulness in doing what we are entrusted to do is important. If we could not be trusted in small things, how can God trust us with big things? Therefore do not worry about the smallness or insignificance you feel in doing what God wants you to do. Because it is through it all the Kingdom becomes real in this world. We all serve the purpose by being faithful and grateful.
Preaching is easy. Share what you love about what you know. If that has anything to do with God, then of course you have begun your preaching ministry right then and there. It is about being connected to yourself that matters and not the eloquence in what you say. You become eloquent by sharing honestly and truthfully what is in your heart to heal, to journey with and to cry with the other. Preach and if necessary use words as St. Francis says.