Are you sure cron is not working? If you add a line like
*/1 * * * * touch /tmp/foobar123
to your crontab, then does the file appear in /tmp?
If that file won't appear after a minute or so, then
ps auxw | grep cron
or
sudo service cron status
If cron is not running, then try to start it with
sudo service cron start
But I guess the problem with your command above is, that gsettings needs to have its environment set up correctly in order to run, which it probably does not have, when run from cron.