Extracting data from multiple columns to one column without duplicates

try this in G...
=IFERROR(INDEX($AC$1:$A$31,MATCH(0,COUNTIF($G$1:G1,$A$1:$A$31),0)),IFERROR(INDEX($B$1:$B$31,MATCH(0,COUNTIF($G$1:G1,$B$1:$B$31),0)),IFERROR(INDEX($C$1:$C$31,MATCH(0,COUNTIF($G$1:G1,$C$1:$C$31),0)),"")))

if you adjust the ranges to cater for additional data, it should update automatically