Mark 16:15-18
And he said to them, “Go into all the world and preach the gospel to the whole creation. 
He who believes and is baptized will be saved; but he who does not believe will be condemned. 
And these signs will accompany those who believe: in my name they will cast out demons; they will speak in new tongues; they will pick up serpents, and if they drink any deadly thing, it will not hurt them; they will lay their hands on the sick, and they will recover.” 

There is no restriction on who the gospel should be preached to.

There is a restriction on who will be saved – it is hinged on belief.

How do you know you believe? Your works.
Your works are a signal to your belief.

Do your works point people to Jesus Christ or to yourself?
If yes, ask for grace to stay the course.
If no, ask for mercy and change course.
If not sure, ask for wisdom to understand your present course.

“‘If you can’?” said Jesus. “Everything is possible for one who believes.” Immediately the boy’s father exclaimed, “I do believe; help me overcome my unbelief!” – Mark 9:23-24

Lord Jesus, I believe, help me overcome my unbelief.