This isn't really an either/or question, but most small businesses get the sequencing backwards — and it costs them.
Ads are a rental. SEO is ownership.
Paid ads produce traffic exactly as long as you keep paying for them. Stop the budget, the traffic stops the same day. SEO is slower to build, but once a page ranks, it keeps producing traffic without an ongoing per-click cost. One is renting attention. The other is building an asset.
Why "start with ads" often backfires
Ads are frequently used to compensate for a site that isn't found organically — but if that same site has weak SEO/AEO foundations, paid traffic lands on a page that converts poorly and never builds lasting visibility. You end up paying indefinitely for a problem the site itself should be solving.
A more honest sequence
Build the site with SEO and AEO foundations first — schema markup, fast load times, clear structure. That work compounds for free, starting immediately and continuing for years. Layer in paid ads afterward, for time-sensitive promotions or to accelerate traffic to pages already built to convert. Ads amplify a strong foundation. They can't substitute for one.
This is why every Index Nations build treats SEO/AEO as the starting foundation, not a service you add later once you're already paying for ads to cover for it.