Yes the gift of the Holy Spirit is very important, that is why Jesus said the disciples have to wait until they received the power of the Holy Spirit so as to give them directions.

This earth is made of the unholy people so to leave and holy life one must buried all his past sins and this is done only through baptisim.

Yes is for all believers. Baptism is an integral part of a believers life.as said in when the Holy Spirit comes to as, it will empower us to move to all nations to preached the gospel.