How to make clients trust you

I suggest you should have a GDPR Compliance certificate if you are storing and processing data. This will add trust to your services. On a casual note, check what certifications your competitors have, this will also help you.

It is a little chicken/egg problem. But, you gotta give something of immense value to some pilot customers, over-deliver, and then get them to give you case studies.

What’s your product ? You could include testimonials on the landing page, or any other kind of social proof eg recommendations of your product that you’ve gained on social media. A badge won’t be as effective as actual results. As a consumer a badge means little to me. What convinces me to buy is the value I perceive.

My experience comes from the decentralized app world, but I think some of it applies here. If you can show good faith by open sourcing your code (not always an option, I know), that goes a long way. If you can put out content showing how the data is used, that helps too. Depending on how your app works, you may even be able to make this a zero-knowledge experience—meaning you as the app developer/company can't see any data but the the customers can.