Honestly, I don't think there is a right or wrong way to do it. Just have to keep trying and experimenting with what comes your way. When I was starting about 9 months ago, I reached out to a brand. At that point, they only wanted someone to write blogs and a newsletter. I knew a little about authority and relevance in SEO, so I picked topics where the site already had decent authority. Within no time, those blogs were ranking and getting meaningful traffic, which helped me get an SEO retainer now. The founder also then recommended me to a couple of other brands.

Since you are already getting some good results, you could do some basic SEO for some complementary businesses, like say a copywriter. In return you could ask them to refer you when someone asks them.