This makes the assumption that we have to be experts to have an impact. The real question is experts in what? Do we all need to be experts in Biblical Studies, Theology, Psychology, and Public Speaking? No. Not at all, you can be terrible at all those and still reach out to people effectively. While I will certainly advocate that we learn more about our faith all the time, and that will make sharing about it more comfortable with more confidence in your own knowledge. Biblically though, that has never been a necessity. Moses stuttered, David had an affair, and Paul initially persecuted the church. To reach out to others we should be experts, of our own faith. You wouldn't recommend a book you never read, you wouldn't try to coach a sport you've never played, you wouldn't lead a discussion on a television show you've never watched. So to share our faith, we first have to live it out in love.