Okay kiddo, so first we need to understand what "economy" means. An economy is like a big system that helps people buy and sell things, like toys or food, so that everyone can get what they need.
Now, when we talk about the "economy of God," we're talking about how God provides for and takes care of all the things in the world. Just like how our parents take care of us by buying us things we need, God takes care of everything in the world.
God created everything in the world, like the birds and the trees and the mountains. He also made sure that there is enough food and water for everyone to have what they need, and that the earth can keep making more of these things.
So even though we can't see it or touch it, the "economy of God" is always working behind the scenes, making sure everything stays in balance and everyone is taken care of. Pretty cool, huh?