Your .htaccess files are not correct. See Here for details
Permissions of folders are not correct. If CakePHP app is Group Writable i.e. 777 then webserver gives 500 error for safety.
You are missing Database Connection. Correct database configuration according to Webhost because most of times local and production server databases have different details.
Delete the content of your tmp folder. It is best practice that you must delete cache if you move your application from one place to another.
For testing purpose debug should be on like Configure::write('debug',2);
If not succeeded check your Apache Error Log. If using Linux /var/log/apache2/error.log
Hope It Helps, Thanks!!