Which tools are most useful for organic marketing?

Recently left startup / corporate world for a lifestyle company. Now seems like an amazing time to build things using AI (which has become freaking amazing in the past few months).

I have built a few MVP apps. What are some of the more useful or innovative tools which can be used for organic marketing?

Hoping to find a mix of AppStore Optimization, Google SERP Optimization, tools to grab attention on TikTok / YT Shorts / IG Reels. Waitlist / interest gauging. Or maybe old-fashioned in-person marketing (posters, merch, etc).