I never buy SEO. Fiverr can be valuable for unusual things that you are not capable of yourself. I would not use Fiverr though for any link building, social sharing, article writing or secrets and tips.
If you are a legitimate website owner with a long term outlook I would say work hard, save up and pay for real quality services with transparency. I have a hard time using Fiverr when someone finds that their work is only worth $3.85 a job.