Kevin DeYoung has a great post about the gospel and the Ethiopian eunuch from Acts 8 over here. 

The gospel really is for everyone.  And when we receive the gospel, like the eunuch, we look back and we start to see ourselves in the story of God's redemption.  We start to see that even while we were still sinners, still unfit to enter God's gates with thanksgiving in our hearts and his courts with praise, while we were still disqualified to number among his people, precisely then Jesus was already at work to remedy this situation through his blood on the cross.