The further back in earlier generations, such as great grandparents, gg grandparents and so forth, that you go, the more likely it is to connect with the big tree. About 80% of the people at WikiTree can connect.
After you have added a few more generations, you may want to exploit the Connection Finder and the Relationship finder. To get there, click on Find (top right of the WikiTree page) and after the Find menu opens, click on Connections.