I have incorporated SEO work for my various WordPress websites by editing meta tags, social implementation with GooglePlus etc., and utilizing proper semantic markup. However, recently I was briefly referred to this company, SML, by a representative. My sites are all already 'mobile-friendly' and I have access to plenty of coupon-generator-plugins, chat plugins, QR barcode plugins, and even "SEO" plugins... all open source. So why should I pay for these services? What are open-source alternatives to their services?
Keep-in-mind, I have very little SEO knowledge aside from editing meta tags and utilizing HTML5 semantics. Can someone with strong SEO knowledge please point me in the right direction towards a better understanding of incorporating the best SEO for various websites such as personal/blog-sites and business/real-estate/retail-sites. Are SML's services worth any price if the services can be done fairly easily for free? Is their 'Directory Submission' exclusively better than personally submitting? Thanks in advance!