1) You don't need 3 recordsets, only 1
2) In the recordset you need to add a where clause to filter the first and last name columns on the entered values
WHERE UserFirstName = paramFirstName OR UserLastName = paramLastName
then in the variables section create 2 new variables as:
name: paramFirstName
type: Text
default Value: -1
Runtime value: <?php echo(isset($_GET['UserFirstName'])?$_GET['UserFirstName'];""); ?>
name: paramLastName
type: Text
default Value: -1
Runtime value: <?php echo(isset($_GET['UserLastName'])?$_GET['UserLastName'];""); ?>