Search Engine Optimisation is an endless task. At the outset, WordPress is one of the most SEO friendly environments to develop a website. Adding SEO plugins such as All-In-One SEO enables even better SEO but there is no end to what can be done, often with diminishing returns.
Content is king in the world of SEO. Google's strategy for scouring the net favours good content. Artificial intelligence matches search phrases and serves the closest matches but also favours other factors such as how many other sites have linked to any given page - (backlinks).
It used to be possible to "keyword stuff" but keywords in the header are largely ignored now. It is possible to build links yourself but Google recognises the quality of the sites from which those links come from and rates your site accordingly. So faking backlinks doesn't work either.
A lot more work can be done on the actual site such as building schemas for each page to help Google interpret each page. Time consuming but this is one of the add-ons I offer to help build SEO.
Google is constantly upgrading its "secret sauce" for rating sites - even employing real people to check that sites are what they say they are. There is a handbook for these real people to follow that is very detailed and if your site is rated badly you can drop in Google rating drastically. Any false SEO tactics on your site, misrepresentation, false backlinks or even keyword stuffing - once detected will result in a downgrade that is very difficult to appeal against.
Be wary of SEO "experts", in my opinion, they're a desperate dying breed clutching at straws to maintain their purpose. Backlinks have always been google's bread and butter analysis parameter and lots will try to sell you various methods tools or whatever. SEO businesses are in trouble because essentially they are redundant, if not actually now, then soon. Google's purpose in terms of search ranking at least, is to give the user the most meaningful search results. They have their secret algorithms and an army of real people who check sites at random and any that suddenly rise up the rankings. Any site caught gaming the system get totally delisted. I have heard of people hiring SEO consultants and getting delisted because those consultants used suspect backlink lists. It takes months if not years to recover. Also they have a rampup strategy now so that your actual ranking isn't gamed from the beginning so that at 15 weeks it perhaps a third of its final 35 week level. So in the beginning interest will seem to build gradually and eventually plateau. At this point perhaps some marketing strategy change might be called for. As an asside google's last algorithm change in Nov 2018 really hit the alternative health sites - so that searching for a specific health problem is no more likely to find the genuine medical sites with reputation rather than the bullshit ones. Of course you can still put in "alternative cancer therapy" and find those if you want.
Anyway, its all about reputation - your content needs to reflect the purpose of the site, it need to be referred to by other sites of reputation. A good way to spend time is when you publish a particular lesson/course/blog - wait a week and then put summaries into Pinterest, FB, LinkedIN etc all backlinking to your site. That week allows for google to "identify" the "canonical" or source as it were. Perhaps you could pay someone to enhance this process but beware of my example about delisting. If you cheat, google will catch you," maybe not today, maybe not tomorrow but soon and" (perhaps not "for the rest of your life" but... 🙂 Buying ads helps but ultimately its down to genuine site reputation. No tricks like buying backlinks or keyword stuffing (even keyword strategies are considered defunct - unless you're are an SEO "expert") work in the long run. Essentially, good content that people will want to read is all that matters.