I’ve had to do stuff like this in the past.
In my case it was a loan processing system, so the master number to work off of was the Account Id. So I created a table, and loaded up 10% of the Account Ids into the table. Then used the records in the table to decide which records to transfer from Production to Development.
Any tables which didn’t relate to the Account Id value I transferred over completely (I’m talking the lookup tables here).