Have you met potential clients yet? Get on the phone, have a face to face meeting with them, and make sure you understand what's the problem they're facing before presenting your solution. Repeat 20 times, then summarize your findings by drawing a value proposition canvas. After you've manually onboarded a few customers, heard their feedback and have a clear sense of which persona uses and buys your product, then you might be ready to start investing in advertising and scaling your go-to market strategy.