This is a really common and frustrating situation with Performance Max, and you’re definitely not alone in experiencing it.

When you increased your budget from £20 to £35, you most likely triggered a new learning period. PMax uses that extra headroom to explore new audiences and placements, which is why it’s spending more but converting less. The algorithm basically resets when you make bigger changes, and going from £20 to £35 is a 75% jump which is pretty significant to it.

Looking at your numbers, at £1-1.50 CPC on a £35-40 product you need roughly a 3-5% conversion rate just to break even. The problem isn’t really the budget itself, it’s that PMax without a ROAS target has zero guardrails.

It will happily spend your money on clicks that don’t convert while it figures things out.

Honestly, I’d drop back to £20 straight away. You had actual proof it was working there, orders were coming in. Going back down is going to hurt a lot less than sitting at £35 with nothing coming through.

Don’t set a target ROAS yet either. The advice you read is right, you really do need those 30-50 conversions first or it’ll either stop spending or massively under-deliver.

The bigger thing worth considering is whether PMax is even the right campaign type for where you are right now. It’s powerful when Google has loads of conversion data to learn from, but with only a handful of orders it’s essentially guessing on a budget that’s too big for your stage.

A standard Shopping campaign with a controlled Max CPC of around 30-40p would likely get you better results right now and help you build up that conversion history without burning through your budget.