What should I be adding to my skillset?

I've been doing dev work for the past 8 years or so, I'm a full stack web & mobile app dev (React, React-Native, Laravel, mySQL). I mostly enjoy working on products for me or startups for clients.

I want to be capable of offering more services to my clients, or learning skills that are more relevant nowadays.

What would be good recommendations? SEO? Social media marketing? Being more comfortable with Python for AI stuff ? Design? etc...

If you can point me in the right direction / provide resources to get started with your suggestion that would also be awesome.

Thanks!

EDIT: I am not necessarily looking for something in the IT field, just something that would make my services as a one man business more valuable