The controllable levers have shrunk
Advantage+ on Meta and Smart+ on TikTok collapsed audience targeting, placements and bidding into automated systems. What remains under your control is the offer, the landing page and the creative. Creative carries most of the variance between accounts in the same category.
That changes where money should go. Production capacity, creator supply and editing turnaround are media levers now. An account producing 30 assets a month has more ways to win than one waiting six weeks on an agency shoot.
Budget buys speed of learning
Spend determines how many conversions you collect, and conversions are how quickly you can call a winner. At a £30 CPA, £3,000 a month buys 100 orders, barely enough to compare four creatives. At £15,000 you get a clean read every week.
So budget matters as a learning rate. Underfunded accounts test slowly, cling to old winners and fatigue faster. The fix on a small budget is fewer tests with more spend behind each, run in bursts.
The ratio that works
Plan 10% to 15% of media budget as creative production cost and 10% to 20% as the testing cell. On £20,000 a month that is £2,000 to £3,000 of production and £2,000 to £4,000 of test spend.
Measure creative output as concepts shipped and win rate. A healthy win rate sits around 1 in 5 to 1 in 10 concepts beating the control. Anything higher usually means your control was already tired.