Hi @Mattw112IG ,
Please try this:
1. First to save the First 6 records, Frist 12 records, and First 18 record to collections.
2. Remove the first 12 records(Col1_12) form the first 18 records(Col1_18), then you can get the records from 13-18.
3. Remove the first 6 records(Col1_6) from the first 12 records(Col1_12)l, then you can get the records from 7-12.
ClearCollect(Col1_6, FirstN('Data Source',6));ClearCollect(Col1_12, FirstN('Data Source',12));ClearCollect(Col1_18, FirstN('Data Source',18));
ClearCollect(Col13_18, Remove(Col1_18,Col1_12));
ClearCollect(Col7_12, Remove(Col1_12,Col1_6))
Then, Col1_6, Col7_12, and Col13_18 are what you want. Try to put the above code to OnStarts property or OnVisible property, and set Col1_6, Col7_12, and Col13_18 to each Gallery Items property.
Hope this helps.
Sik