In order to have a quick win, you should read the source code for
Services
1. Web site(s) files (source codes) that you have just exploited.
2. Configuration files:
Apache
/etc/httpd/conf
/etc/httpd/conf/httpd.conf
/etc/apache2/httpd.conf
/etc/apache2/apache2.conf
Nginx
/etc/nginx
/usr/local/nginx/conf
/usr/local/etc/nginx
php
check with phpinfo()
3. Database that the web site is connected.
4. Home directory for the user that you have currently logged in.
5. Any other locations such as /var/log /var/backups, etc.