You should be building this out in a demo account. This will not only help you exercise the knowledge that you have gained thus far, but provide some valuable practice testing things out so see if you have made any mistakes or if there was a way your system could have been designed in a way which reduced user error or the number of steps required to accomplish something.
The best way to test things out is to run records through everything you have set up to see what the user experience is going to be like on the front end. Then utilize workflow rule logs, record timelines and audit logs to make sure everything is operating correctly.
If there are multiple criteria that can be applied to a record, like multiple options in a picklist, those each need to be tested.
