The wheel group is used to control those people that can su to the root user (though this is made irrelevant by the sudo command).
All of the users on your system will be in the staff group, so by changing group ownership of files to staff the group permissions will apply to all users. All of the administrators on your system will be in the wheel group, so by changing group ownership of the files to wheel group permissions will apply to all of the administrators, global permissions will apply to any other users.
My advice is that, except for files that you have created, you leave the group ownership and permissions alone. Unix is very particular about file ownership and permissions in certain areas and changing them only leads to trouble.