What marketing channel gives you the best ROI?

If you had to rely on just one marketing channel to grow your business, which would you choose?

If I had to pick just one, I'd go with SEO. It takes longer to get results, but once your content starts ranking, it can bring in consistent traffic without paying for every click. I've found it's one of the few channels that keeps working in the background if you continue publishing quality content. That said, I'd still build an email list from that traffic because relying on any single platform is risky in the long run.