Hi Zee,
In addition to the links that Binesh has suggested, I have a couple more recommendations:
1. If you work for a company that owns a NAV license and is current on the Enhancement plan, you can access the e-Learning modules for Dynamics NAV from the Microsoft CustomerSource portal. The e-Learning modules include courses on general system use, Financial Management, Trade, and much more.
2. There are also some books written by NAV experts that you can purchase from publishers like Packt. Here are some titles that may interest you, and are fairly inexpensive (as little as ~$25, and none of these are more than $90). You can get them in eBook or paperback format.
There are many more books on NAV at Packt Publishing, and you can also find more on Amazon.
Lastly, join NAVUG (the worldwide NAV User Group), if there is a NAVUG chapter in your region, I advise you to participate in that as well. NAVUG routinely hosts webinars for free, and also conducts 2-4 hours Academy courses throughout the year on various topics in NAV, including Financial Management.
I hope this helps. If my response has answered your question, please verify by clicking Yes next to "Did this answer your question?"