Need suggestion seo plugin

I am ready to put my site online soon. In my theme (site) I do not use single.php file as all my posts are viewed on index.php. 2 posts per page.
it is a magazine, so two articles then you flip the page and so on.

I am looking for suggestions, from you guys, on which plugin to use in my case. I really try to be minimalistic with the code and I hope that the plugin not bigger then my site.

Thanks