It would be difficult to point out the area of "the most need" spiritually and physically. It could be North Korea, but you can't go there.

I would have a different suggestion.

1) Get involved where you are right now. Ask your pastor or knowledgeable Christian friend where there is the place of the greatest spiritual and physical need in your community. Find out how you can get involved. Begin to learn how to help people. Study a bit about how these needs can be met. Ask the Lord to teach you. 2) As you serve in this place, ask the Lord to bring you into contact with those who are serving in even needier places. Read mission magazines. Listen to the missionaries who come through your church. Begin to discover your spiritual gifts, what gives you joy as you serve. 3) Little by little, you will find that the Lord may touch your heart with a place of even greater spiritual and physical need. But now you will be more ready to truly help. You won't be as idealistic, but more realistic. You will learn more about what you can do and what you can't. 4) As you begin to project yourself toward the place of service where you think the Lord wants you to go, incorporate others in your vision. Gather people around you to believe in you (as they see what you have accomplished) and want to be part of your vision. Find a mission agency that can orient you and establish you in this. You may have to learn a foreign language, but this will be your entrance into the new culture. 5) As you begin to move into the site of your vision, you will thank the Lord for all He taught you along the way. You will be ready to make a true contribution in a difficult place.

May the Lord help you get started.