Speaking in Tongues is progressive through The Spiritual Gifts to fulfilling The Great Commission.
In Acts chapter 22, Ananias confirmed to Saul that he had been chosen by the Lord to be a witness for Jesus Christ unto all men. He said to him what are you waiting for? "paraphrased" "Arise, and be baptized, and wash away thy sins, calling on the name of the Lord." Saul becomes Paul. He became a believer in a most extraordinary way. He believed, repented (Acts 9:6), was baptized, filled with the Holy Spirit and spoke in tongues. He co-labored with the Lord in the manifestation of The Spiritual Gifts and began fulfilling The Great Commission.
The pattern and instructions for the Church in these things are clear.
Speaking in tongues is the threshold or gateway into the Supernatural for the believer. It signals the point where God completes a two-fold process of residing within the believer for a Spiritual life and development (John 14:15-17) and upon the believer for power (Acts 1:8) and ministry.