You don't have to choose between conversion and SEO. There are some techniques you can use that are beneficial for both!
Utilize up-selling, and cross selling on your website and spend some time focusing on your call to action. Both can help with SEO and conversions.
As you probably already know, great content is extremely important to build a relationship with your audience and with search engines! Convince and Convert said, "Writing your landing page copy is not different than writing any digital content. It needs to be readable, concise and clear."
Finally, start working on your social proof and continue to interact with your customers after a purchase.