Order / Priority of development in Symfony

So I've decided after much debate and research to use symfony on my next project. To sum the project up, it is an LMS (Yes, I know there are pre-built ones such as moodle but they do not have what my particular company requires). There are many modules and issues to take into consideration. My question is in what order should one start with Symfony?

Note, the database is already made and populated with data.

The Doctrine ORM? User Authentication? Creating the Core modules? (Courses, Enrollment, Grades) Page security (i.e. installing the rules for who can access what page)?

Checking out the Jobeet tutorial is good advice.

If the database is already built, I would probably do something like this:

• Ensure you have a plan of what "objects" and functionality the site is to have (eg. list of courses, course detail page, course search, etc). You should be able to visualise the site and have some design mockups ready. It would also help to know whether it's going to be multi-language or not.
• Generate Doctrine models & form classes on the back of your db
• Create home page placeholder (probably a module) and a logged-in home page placeholder (probably a module) + basic layouts for further tweaking later.
• Create signup & authentication processes (so you have the core functionality of adding users, signing them in and signing them out). Use sfDoctrineGuardPlugin.
• Now, start creating core modules one by one according to your plan. As you progress, you'll notice what bits make sense as partials/components and where an additional module might make sense. Add new routing rules as you go along.
• Finally, add any little bits, cleanup your template HTML/CSS, JS files, etc

... this way you have a work-in-progress site that you can play around with as you go along.

If I were you, I would try to follow this tutorial : http://www.symfony-project.org/jobeet/1_4/Doctrine/en/ You can certainly match each step of the tutorial with a feature your website has.