There is no universal number — entry-year budget depends on category, competitive intensity, and whether you are chasing brand awareness or direct-response pipeline. The more useful framework is to split budget across three phases: a small validation phase, a scaled build phase once demand is proven, and an ongoing run-rate once the engine works.
Resist front-loading spend before validation — most entry-year budget mistakes come from scaling a channel mix before it has been proven at small scale. Size the budget to the plan, not the other way around.