The first gospel preacher Jesus sent out (the twelve) their work was the same as that of Christ – because they preached the kingdom and Jesus always confirmed what was preached.
Announcing the kingdom of God without accompanying signs is simply a motivational message. This is what happened when the twelve went out to preach. The Bible says:
" And they went out, and preached that men should repent. And they cast out many devils, and anointed with oil many that were sick, and healed them.” (Mark 6:12-13)