Thinking about this from a 'what Google say they want' point of view then your wish to not rely on content means you've lost before you begin IMO.
Google doesn't know who the best web designers are, and it has no way of figuring this out. What it DOES know is who the most noteworthy and cited web designers are.
The way you become noteworthy is to be cited by others - especially in your niche. You don't do that by asking for links. You do that by becoming a recognised expert and a business / person of note. You do THAT by being active in your niche. That means being seen to talk authoritatively about your specialist subject, getting your name and your brand out there. That leads to citations, these confer trust on your site and it ranks for its key terms.
There is no way around this if you want to 'play it by the rules'.
If you wanted quality referrals for your business offline, how do you think you'd get these? You have to apply those same principles online.
The library here is full of great ideas. If you haven't already I suggest you spend a few days reading it. You should end up with plenty of ideas and inspiration.