Increase my website sales Marketing Guru

I have an established website selling a nutritional product. Sales are steady and mostly come through from Adwords. I want a Marketing Guru/Expert to increase my sales at least 50% and preferably 100% Please note - I will pay based on meeting the sales growth and not just for some link building etc. I want someone serious - focused who can be asset to my company and help grow. Look at my feedbacks and you will see i am good employer and expect decent freelancer. In your PMB - please provide your marketing ideas in how to increase the sales - cost structure etc. Again: I will pay only based on success on sales growth and it is already a good selling website and can sell a lot more with a good marketing person. P.s: I will not respond to generic bidders from SEO fellows that offers fast food kind of service. thank you.