Invoice Approval starting with supervisor followed by an approval group

Summary:

Dear folks,

We have a requirement such that all invoices should be routed initially to the requester's(requester in invoice page) immediate manager(single level) and once he/she approves, it should route to an approval group in Parallel First Responder Wins manner.

Content (required):

I would like to know the rules and rulesets that need to be used to achieve this functionality. Please share your inputs in this regard. Thanks in advance

Version (include the version you are using, if applicable): Rel 13

Code Snippet (add any code snippets that support your topic, if applicable):