Don't fall for, "If you build it, they will come."
You're getting close to launching your product (or maybe you already have) and now what's keeping you up at night is developing a large enough user base to meet your next round of goals (testing, funding, revenue, etc.) I'll provide you actionable insight on how to grow this user base, what to expect in the process and how to set realistic benchmarks.
There is an intersection of marketing elements - programmatic, Marketing Automation, SEO, SEM, Social, growth hacking, content strategy, and traditional marketing that form an appropriate mix that will drive adoption of your product/service. What's difficult is prioritizing how to spend limited funds and time.
While there is no single answer at what that mix should be, the process to arrive there doesn't change. I have gone through this process for companies as large as Dreamworks Animation, trying to drive adoption of their Kung Fu Panda MMORPG, to driving downloads of apps and browser extensions, to a wide range of ecommerce including my own company, Hot Sauce Adventure Club.