I wouldn't spend ad dollars at launch. It's way too risky and costly to do at any kind of meaningful size. Instead, I'd soft launch the app by finding as many early-adopter / reviewers as possible. Regardless of what you're building, there are people who will provide you feedback and write about you if they've had a positive experience.

Conversely, you might find that there are some critical product gaps or issues that need addressing before you spend money to acquire less friendly (i.e. forgiving) users.

The bottom-line is that before spending real customer acquisition tactics, you should exhaust all outreach efforts to build a small but vocally supportive community of users.

Happy to talk to you about what you're building and provide more specific advice but the advice above is applicable in 99% of app scenarios.