As far as I remember, I didn't hire anyone, I just kept reading and testing for some time and I got it working. But in my experience, you never stop tunning, there is always something that you can tune up and improve.
These are some documentation links that helped me:
http://dak1n1.com/blog/12-nginx-performance-tuning/
https://www.nginx.com/resources/admin-guide/restricting-access/
https://www.nginx.com/blog/mitigating-ddos-attacks-with-nginx-and-nginx-plus/
https://www.nginx.com/blog/tuning-nginx/?_ga=1.31581114.52852353.1448923185
https://www.ruby-forum.com/topic/6878679
https://www.nginx.com/blog/http-keepalives-and-web-performance/
http://stackoverflow.com/questions/36640216/nginx-what-is-nodelay-in-http-request-limit-module
https://github.com/lebinh/ngxtop
If you are looking for someone to hire, you can check upwork.com, there are plenty of experts there.
Regards,
Lisandro.