Topic: Gem suggestions needed - Accounting, Workflow, project management

I am developing my first Rails app for a Residents association community management. Need gems to do:
1. Simple accounting, invoice, billing, book keeping. Prefer api wrapper to industry standard software
2. Simple project management.
Any recommendations?
Finding it difficult to narrow results with google since any project management is converging on software project management, not much luck with team or workflow etc either. Not sure about quality of the gems for accounting since they do not seem to have any documentation.
Thank you,
- Jayawanth