Well what works best is Google Search ads, its expensive but they deliver new users non-stop and I was able to drive down the cost per lead a lot. Besides that post on free platforms like Reddit, Twitter, Facebook into relevant groups and tell them about your tool or service.

Do SEO, but only low cost SEO. Don't buy expensive guest posts, instead you can offer to provide great content in exchange for a backlink to your website.

Create a lot of content for marketing and post on popular platforms like Facebook, Twitter, Reddit, Tiktok, Linkedin, Instagram & Forums.

Leverage your network. Reach out to your network of friends, family, and colleagues for advice, support, and resources.