Product SEO first
Every product carries an SEO title, a meta description, a product handle, per-image alt text and (via metafields) structured data. Filling these fields well across the whole catalog is worth more than any single blog post. Left blank, Shopify fills them with defaults that rarely match search intent.
Technical hygiene
Schema.org markup, canonical URLs, sitemap correctness, hreflang for multi-region, robots.txt discipline, alt text on every image, internal links between related products. None of these are exciting, all of them compound.
Scaling with formulas
Filling SEO fields one product at a time doesn't scale past a few hundred SKUs. The practical approach is a formula per field, applied in bulk and re-run whenever the underlying data changes.