Start with the objective
A campaign budget should follow the objective rather than being chosen independently. The amount an advertiser can spend is only useful when connected to what the campaign is intended to achieve.
Separate testing from scaling
A sensible campaign strategy often begins with controlled testing. The goal is to learn which inventory, targeting and pricing conditions produce acceptable results.
Scaling should happen after there is evidence that the campaign is working rather than simply because more budget is available.
Watch delivery
A budget that is technically large enough does not mean the campaign will spend efficiently. Delivery depends on eligible inventory, competition, targeting and bid conditions.