Resigned two months before still not receive full ad final settlement?

Hi, I worked for a company at the start of 2015 for 5 months. When I joined, I signed an offer letter, and was promised an Appointment Letter on joining. I never got the Appointment Letter but I didn't insist or follow-up aggressively, because the owner was also a close friend. I resigned within 5 months through an official email, citing reasons that were duly acknowledged. It has now been 8 months, and I still haven't received my F&F settlement or any exit documents, despite regular follow-up. What are my options? Is it worth litigation, and what time/resources will it cost to sue?