If you haven't used redmine before, you'll probably just have to start using it, familiarize yourself with the different options it offers and adapt it to your particular needs later on.
I strongly suggest creating either a redmine project for each client or for each client project:
Create one redmine project for each client if
- your client work isn't project based
- you have lots of very short projects
- you'll plan having only a few tickets per client
Create one redmine project for each client project if
- you're client work is project based
- a high volume of tickets is to be expected
- you have several projects for one client
- you have a different POC at the client for each project (you may want to give access to a client for her project only)
- projects are limited in time (you may close inactive projects)
- reporting by project is needed
You can view open tickets by priority - I recommend creating a custom filter for this purpose. This filter can then be used on a global level to view all tickets of all projects as well as within a single project.
In order to create new tickets rapidly, you may want to save a shortcut for each client if you feel that navigating to that page takes too much time. Otherwise, you may configure the text of redmine's start page with useful links. There's also the possibility to setup issue creation by email. I personally find that navigating to the new issue page of a project is quite easy with redmine.
Feel free to change the trackers and their names. You may find that a single tracker is all you need. Reasons for multiple trackers may be:
- Reporting
- Different workflows
- Limiting access
In general, I recommend to keep it simple, especially in a 2-man shop.