forces of the Gentiles (Isa. 60:5 KJV, Isa. 60:11 KJV; Revised King James Version, “the wealth of the nations”) denotes the wealth of the heathen

Compare: Isa. 60:5 NASB; Isa. 60:11 NASB

The whole passage means that the wealth of the Gentile world should be consecrated to the service of the church.