I need freelancer for long term seo (both onsite , offsite)

I have an ecommerce website (opencart based) up and running since more than a year.

I need someone who can handle complete seo from scratch including keyword research, onsite improvements, article writing , submissions etc.

Initially It should be done for atleast 10-15 keywords with good traffic and going forward we will increase the keywords.

Also I need someone for long term and committed to provide results. Others one time works please don't contact.

Also I want to pay fix amount every month. I am open for any other suggestions.