Have you checked out the "invoices" starter solution included with filemaker. It may offer some pieces and parts that translate well for your solution. Also, you should go through the basic (free) and advanced ($19.99) filemaker training series to understand the core concepts of using FileMaker.
You'll find better help here if you have specific questions, rather than vague "check out my file" posts. While I'm sure a lot of us would be willing to help you, our time as mentors and trainers is valuable to us as well, and hiring a mentor consultant would be more appropriate if you're looking for someone to train you.
What's your end goal for FileMaker? Are you only interested in using it for your own solution (casual development), or are you interested in possibly developing solutions for others as well (consulting development)?