It won’t be the theme itself…SEO, especially nowadays is based around the basics such as:
- page load times
- using keywords appropriately in page content
- using keywords in headings
- using keywords in link text, titles, etc
- using keywords in image ALT tags
- don’t over use keywords (no spamming yourself)
- making sure your keywords are related to the page content
- utilizing style elements on keywords like bold, underline, etc.
- linking only to authority quality based websites
- getting others to link to you, preferably the quality sites as mentioned
- keeping your site active with regular flow of content
- try to avoid too many code errors…some are fine if any, but if your site is loaded with them, this can go against you.
- Involve social networking, sharing of content, etc
You should test your site with this online tool: Speed Test
You also want to make sure that your own site is not a mix of different subject matter, such as talking about apples then suddenly oranges, then grapes, then back to apples. In a nutshell, you want your site to become an authority of a topic or subject matter that offers quality content…something that gets people talking about on social media, bookmarking your site, something that becomes popular (being an authority).
Check out this plugin that apparently is popular: Yoast But of course, there’s other ones too.