What have I learned so far?

1. Getting people's attention on the internet is very difficult.  Try posting a lync on a Google+ community that you think matches your target audience and see how many people visit your site as a result.  Probably one or two people at most.  If you're going to paid route, it might be tempting to go with a service offering a lower cost-per-click than GoogleAdwords, but in my limited experience the less expensive services provide lower quality traffic.  Now I see why so many sites offer free content to attract attention.
2. SEO is easier for static content then for dynamic content.  There are some amazingly ugly websites - poorly laid out and with tons of ugly ads, that do quite well.  Try googling "middle school math" and you'll notice that the first hits are just pages of links to other content.

Combining facts (1) and (2), I'm thinking that for my website, it would be best to create some static content that is free and open to the public.  In my particular case, I will use my web app to create some freely available HTML & PDF math worksheets.  Easier for Google to crawl (though it is possible to get Google to crawl JSON), and (just as important) other sites are much more likely to want to link to free content.... more links means improved search results.