First off: you've got this! I'm sure lots of people on HN have felt this way (:hand-raised:)
My approach is roughly: "getting out of my comfort zone" + repeat what worked and drop what doesn't.
With a BIG caveat that this is all running off my own money, not investors. I get tempted by marketing/sales tools (eg: apollo.io, za-zu), vendor exhibitions, paid ads, etc but if I'm not fairly certain I'll get the $-spent back, I do the free/harder way first until I understand that system more. Dollars can give leverage, but aren't certain to.
Also, publicly track the experiments you run as an accountability system (and doubles as a bit of marketing for your product)
EG:
Scroll down on 24HourHomepage.com to see a history of how I've thought about growing it roughly week over week
Its really because on the back of my mind I was wondering if there's a way to have revenue without intrusive advertising or anything.
And, inspired by the games industry where people seem very willing to buy digital good to make their characters look good, I thought well thre are people on the internet who really value having exactly the username they want. And then I thought well maybe I should hold off giving away what might be a practical, non intrusive way to generate revenue. Thus I though, well the easy way is just to put a number on the end of the username. That's the thinking. If you've signed up, as an early joiner I'd be happy to give you your username without the number - email me at developers@crowdwave.com and I'll fix you up.
I personally think that's pretty cool. Also fixes the squatting issue that otherwise would undoubtedly happen.
I do wonder whether a big company could sue you to give them the account for free on the premise of this being 'blackmail'. Might be something to keep in mind. But once BigCo sues you for this, you probably don't need their money anymore ;)