There is no universal number — budget should be set as a function of your break-even CPA, not a rule of thumb like percent of revenue. Work backward: know your margin, your target CAC, and how many qualified leads or sales you need monthly, then size spend to hit statistically meaningful volume per campaign, not just a headline figure.
In the UAE, expect to fund a testing phase across Meta, Google, and possibly TikTok or Snapchat before committing most of the budget to one channel — Dubai and Abu Dhabi audiences are competitive, and CPMs vary by industry and season.