The Most Common Google Ads Mistakes and How an Agency Avoids Them

With new clients, we regularly see the same problems. Not because the previous management was particularly bad, but because certain mistakes happen structurally when Google Ads isn't managed with enough depth and experience. The good news: most of these mistakes are avoidable.

Working with online shops, we regularly see the same problems with new clients. The good news: most of these mistakes are avoidable if you know what to look out for.

Mistake 1: Faulty or incomplete conversion tracking

By far the most common mistake we see lies in tracking. Roughly three quarters of all accounts we review in an audit have measurable tracking problems.

Mistake 2: Performance Max without brand exclusion

By default, Performance Max cannibalises brand searches you would have captured even without ads. That systematically inflates ROAS.

Mistake 3: Messy shopping feeds

The product feed is the strategic heart of Shopping campaigns, yet it's often treated as an afterthought.

Mistake 4: Too few negative keywords

Without systematic maintenance of negative keyword lists, every Google Ads account burns budget on irrelevant search queries for months on end.

Mistake 5: Wrong bidding strategies for the available data

Automated bidding strategies like Target ROAS need a certain volume of conversion data. If a campaign gets only a few conversions per week but runs on Target ROAS, you get chaotic fluctuations.

Mistake 6: Everything in one big campaign

The impulse to cram as much as possible into a single campaign produces campaigns that can't be steered strategically.

Mistake 7: Orphaned or broken ads

In many accounts we find Responsive Search Ads that were set up months ago and have been running unchanged ever since.

Mistake 8: Ignoring margins

Many agencies optimise Google Ads exclusively for revenue KPIs, without accounting for the fact that different products have different margins.

Mistake 9: Retargeting without exclusion logic

Retargeting without excluding buyers means your budget flows to people who have just purchased.

Mistake 10: Missing balance between acquisition and retargeting

Because retargeting shows high ROAS figures, budget gets shifted towards it. Acquisition quietly shrinks.

Mistake 11: No seasonal planning

Many shops run Google Ads on the same pattern all year round, without structurally preparing for seasonal peaks.

Mistake 12: Inadequate documentation

Many agencies work largely undocumented. Decisions aren't recorded, tests aren't documented.

Conclusion: most mistakes are systemic, not individual

The mistakes we keep finding in accounts are rarely the result of individual incompetence. They're the result of systemic problems: too little time per account, too shallow an onboarding, too superficial processes, too little specialisation.