If you need customers this quarter: ads first — they're the only channel with a same-month feedback loop, and the search-terms data they produce teaches you exactly which phrases convert (intelligence SEO then uses).
SEO compounds and eventually out-economics paid clicks, but on a 6–12 month clock; funding it first means paying now for revenue later while the doors need customers today. Sequence, don't choose: prove demand with ads, reinvest into SEO for the proven terms, let organic gradually shoulder the load.
The exception: if your market's CPCs are brutal and your break-even math fails the calculator, SEO-first (plus reviews/GBP for local) isn't patience — it's the only viable route.