Do you feel like you’re wasting advertising budget on underperforming Google Ads?
Time and time again, we see Shopify merchants making the same mistake with their Google Ads. They set up PMAX campaigns and hand over the reins to Google straight away, before training it in their product catalogue or what “good performance” looks like for their store.
In 2026, Google Ads is heavily driven by AI, especially PMAX campaigns. But AI is only as smart as the data you feed it. So, if you haven’t trained the AI in what it is you’re trying to achieve, chances are it’s not going to perform how you want it to.
Here at Create8, our team of PPC specialists has helped countless Shopify stores to optimise their Google Ads campaigns to reach the right audience and optimise their return on spend.
In this article, we explain why your Google Ads are underperforming and what you can do to fix them and start getting better returns from your PPC budget.
What is the number one mistake Shopify stores make with Google Ads?
The most common mistake we see Shopify stores make with Google Ads isn’t overspending, a poor creative, or even weak products – it’s giving Google full control before it has earned it.
Many Shopify merchants use PMAX campaigns because they’re so easy to set up. They launch one campaign, which they upload their entire catalogue to, then they choose a Target ROAS (return on advertising spend) and leave Google to figure out the rest.We get it, this may seem like the quickest and simplest route – but it’s not going to achieve the best return. Instead, you need to train Google
Ads before you can trust it to optimise your campaigns effectively.
Why does Google Ads need to be trained?
PMAX campaigns aren’t designed to replace strategy; they’re designed to scale proven performance. The problem is, Google doesn’t automatically know what “good” looks like for your store. It can only optimise your campaigns based on the conversion signals and data it has access to. Without being trained, it doesn’t understand your margins, stock priorities, or which products you want to scale. If your PMAX campaign only generates sales on a handful of products and some products have no conversion history, it will concentrate on whichever products have sold.
What happens if you skip the training phase?
When you put your entire product catalogue into a single PMAX campaign, Google will put more budget into the products that convert fastest and are most often searched for – basically, the products it has data for. So, if only five of your products get traffic, Google will assume only those five are good.
This creates a cycle where a few products get all the traffic and so generate all the data, and your other products fade into the background.
As Jack Kinder, Lead PPC Specialist at Create8, puts it:
“The biggest mistake I see is ‘Lazy PMAX’—dumping every product into a single campaign. That is just donating margin to Google.
You have to force Google to work for you and not spend your money as it wants. Make sure it’s receiving data, then build that conversion data across your products before you give Google more control than it has earned!”
Three steps to fix underperforming Google Ads campaigns
Are you ready to start getting better returns from your PPC budget? Follow these three simple steps to ensure Google has access to all the data it needs to understand your product catalogue and start spending your ad budget more effectively.
Step 1: Enable server-side tracking
Browser-side tracking is no longer enough. If you don’t yet have server-side tracking set up, then this should be your priority. Browser tracking is less reliable now because of cookie restrictions, iOS privacy changes, and ad blockers. Server-side tracking sends data directly from your server to Google, making it much more reliable.
Contact our team of Shopify specialists here at Create8 for help getting set up with server-side tracking.
Step 2: Train Google on what you want to achieve
Next, you need to train Google on your product catalogue and which of your products you want to scale. You do this by running manual campaigns, rather than dumping all of your products into one PMAX campaign.
Set up manual search campaigns (without AI MAX enabled)
Set up a manual search campaign for each product type, allocating budget based on profit margin and search volume. Set the bidding strategy to Maximise Clicks with a Max CPC to build clean data.
Set up manual shopping campaigns
Split your products by either ROAS performance or search volumes. Again, set budgets based on profit margins or search volume to Maximise Clicks.
These campaigns are now set up to allow each product to earn clicks and conversions and generate conversion data across your whole product range.
Once each campaign has at least 30 conversions in 30 days, you can switch bidding to Max Conversions. Then, eventually, once the majority of your campaigns have moved to Max Conversions, it’s time to launch structured PMAX campaigns.
Step 3: Structure your PMAX campaigns
Once you’re confident that Google has sufficient conversion data, you can finally begin setting up your PMAX campaigns and giving back some control to Google.
Instead of launching one PMAX campaign, set up one High Performance PMAX for your top ROAS quartile products and one Mid Performance PMAX for your next best quartile. This helps to avoid your high-margin products from subsidising the poor performers and budget being wasted on weak SKUs.
Set the Target ROAS bidding strategy to around the current performance in the manual campaigns, but be ready to scale this up in line with the campaign’s actual performance.
If PMAX is doing its job properly, you should expect to see it achieve a higher ROAS than your manual campaigns.
Don’t forget to keep reviewing your campaigns and be ready to graduate or demote products from the high-performance group to the mid-performance group and vice versa according to performance.
Important! At this point, many people make the mistake of switching off the manual campaigns – believing they have done their job now. Do not switch off the manual campaigns! It’s important to keep them running as they are feeding your PMAX campaigns with the conversion signals they need to perform well.
A checklist for troubleshooting poor Google Ads performance
If, once you’ve followed all the steps above, you’re still experiencing poor performance on certain products or campaigns, use this handy checklist to help you get to the bottom of the issue.
- Is the data tracking broken?
If conversion tracking is broken or under-reporting, Google won’t have the data it needs to optimise effectively. Test your conversion events and compare the reported sales with Shopify revenue to make sure tracking is accurate.
- Has the product been disapproved?
Look for the product in the Google Merchant Centre or in the Products menu in Google Ads to check for any disapprovals, warnings, or limited eligibility that may be stopping it from appearing in Ads.
- Are the product titles and descriptions optimised?
Google relies on the information in your product feed to understand what it is that you’re selling. Poor or vague titles, missing attributes, or poor product descriptions will all limit a product’s visibility in search.
- Are the products priced competitively?
Search for your own products on Google and then compare your listings to your competitors’. Check if your pricing is competitive and whether they are offering customers anything extra that you’re not – like free shipping.
- Is Google diverting spend?
In Google Ads, look at the Products menu to check how much that product has spent over the last 60-90 days. If certain products are receiving little or no spend, Google might be diverting spend to other products because it has limited data or because they’ve not performed well at the start of the campaign. Consider separating these products into a separate campaign to give them a chance.
- Is your product page UX killing conversions?
Even the best campaign can’t fix a poor user experience. If your Shopify site speed is poor, CTAs are unclear, or if important store policies are difficult to find, your conversion rates are going to suffer. Use tools like Microsoft Clarity or heatmapping tools to help uncover friction points.
Often, when a Google Ads campaign is performing badly, there is more than one problem at play. Take the time to troubleshoot and fix the foundation, and you will find that performance improves dramatically.
Partner with Create8 for help building optimised Google Ads campaigns for your Shopify store
In 2026, Google Ads relies heavily on AI, but to achieve the best results, your PPC campaigns still need strategy, structure, and hands-on management.
Automation only works when it’s built on a strong foundation. There’s a lot of prep work to do before you can hand over control to Google.
At Create8, our PPC specialists help Shopify brands to implement server-side tracking, structure Google Ads campaigns strategically, and use automation the right way.
If you’re ready to start achieving better return on ad spend with your PPC campaigns, contact us today by calling 0161 820 9686 or emailing hello@create8.co.uk.
