What is the best traffic source for search arbitrage?
There is no single best source. Meta (Facebook and Instagram) is the most widely used for Google RSOC because of its reach and bidding tools. Taboola and Outbrain suit article-style pages. TikTok offers cheap reach with fast creative burnout. The right choice is whichever your feed approves and where your revenue per visit stays above cost.
Compare sources on four things: price (CPC), the intent of the people clicking, how strict ad review is, and whether the feed gives traffic source approval. Paid social has the best automated bidding once revenue is passed back. Native advertising gives control at placement level but needs constant blocklisting. Google's own Google Demand Gen inventory is high quality but closely scrutinised.
Cheap sources such as push notification traffic and pop traffic look tempting on price and are commonly refused by Google-based feeds because of their invalid traffic and accidental-click rates. Start with one approved source, learn its rules thoroughly, and add a second only when the first is stable, both to grow and to reduce concentration risk.