How to create content when your keywords are about selling services

Hello,

I have a website for web development services. I created pages to rank locally on long tail keyword like "web dev my_city" but people keep telling SEO is about creating content as well to rank.
But what keywords shoud I choose ? I can't create dozens of articles around "how to find web dev in my_city".

And I can't create content around how to create a website, since my client don't want to learn to create a website but want someone to do it instead.

So is content marketing for SEO worth it for me ? What to do when your keywords are about your business and not what you offer ?

Thanks !