Myra's Ocean Outlet is Myra's CastleVille Legends Market located in the Sunnyside Cove section of your kingdom. Here she buys items made with turquoise, stone, and other items unique to Sunnyside Cove (or levels thereabouts), such as Kraken Fangs and Goat Milk.
As far as strategy goes, I hustled to get access to Myra's Ocean Outlet, since selling to Myra is a primary method for raising funds, and every new market brings new opportunities. However, until you have a Turquoise Mine in place, there's not much point.
You can make a few things from stone (which at that point you will only be able to get via mining boulders, which is slow and expensive to be sure, since they're a finite resource), but most of what she wants is made with turquoise. So once you have purchased your Turquoise Mine (and are waiting the two days for it to build...sheesh!), then start working your way to this market.
First available at level:
Cost to claim parcel of land:
800 Royal Coin