Fix Auction Overlap: The CBO & ABO Ad Structure Blueprint

I’ve audited hundreds of ad accounts over the last few years, and there’s a pattern I see almost every single time. It doesn’t matter if it’s a small e-commerce brand doing £5k a month or a SaaS company spending £50k. The account usually looks like a bomb went off.

You’ve got a campaign for "Cold Traffic - Interest A", another one for "Cold Traffic - Lookalikes 1%", another for "Retargeting - 30 Days", another for "Retargeting - 180 Days", and maybe a random "Test Campaign" from three months ago that someone forgot to turn off. It’s a nightmare to manage, and more importantly, it’s actively hurting your results.

If you are struggling to lower your Cost Per Acquisition (CPA) and you feel like everytime you try to scale, your results tank, the problem is likely your structure. You are probably making your campaigns compete against each other, driving up costs and confusing the ad platforms.

I’m going to walk you through exactly how to fix this. We need to move away from the "granular control" mindset of 2016 and embrace a consolidated structure that actually works with the modern algorithms.

The Myth of Granularity

Back in the day, we used to create single-keyword ad groups (SKAGs) on Google or super-specific interest ad sets on Facebook. We wanted to control exactly who saw what. It felt smart. It felt like we were doing "proper marketing".

But here's the honest truth: the algorithms are now smarter than us. They have thousands of data points on users that we don't see. When you slice your audience into tiny little chunks, you are effectively starving the machine of the data it needs to learn.

Facebook (Meta), Google, TikTok... they all need *conversion data* to optimize. If you have your budget split across 20 different ad sets, none of them get enough conversions to exit the "Learning Phase". You end up paying a premium for unstable performance. I remember working with a Medical Job Matching SaaS where we consolidated the budget and optimized the structure. This allowed us to reduce their Cost Per Acquisition (CPA) from £100 to just £7. No magic tricks, just better structure.

And this leads us to the biggest issue: Auction Overlap.

What is Auction Overlap and Why It Kills Scale

When you have multiple ad sets targeting similar audiences (e.g., "Small Business Owners" and "Entrepreneurship"), you might think you are casting a wider net. In reality, you are often bidding against yourself.

But it's not just about driving up the price. The ad platforms (especially Meta) have a feature called "deduplication". If two of your ad sets enter the same auction for the same user, the system simply stops the worse-performing ad set from bidding.

This sounds helpful, but what actually happens is that your campaigns become unstable. One day Ad Set A wins, the next day Ad Set B wins. Your performance fluctuates wildly, and you can't scale because as soon as you increase budget, the overlap increases and performance tanks. This is a classic case of how to avoid auction overlap when scaling CBO campaigns.

The "Golden Standard" Account Structure

So, how should you actually set this up? For 90% of businesses (Lead Gen or E-com), you only need a simplified structure. This isn't lazy; it's strategic. We want to give the algorithm "liquidity"—the freedom to find the cheapest conversions within a broad container.

Here is the structure I use for almost every client initially:

1. The "Scaling" Campaign (BAU - Business As Usual)

This is your main driver. It should hold about 70-80% of your total budget.

• Campaign Type: CBO (Campaign Budget Optimisation) / Advantage+ Campaign Budget.
• Why CBO? It automatically shifts budget to the best performing ad set in real-time. If you try to manually control budget at the ad set level (ABO) for your main scaling campaign, you'll likely act too slow compared to the AI.
• Ad Sets: Keep it simple.
  • Ad Set 1: Broad (Just age, gender, location). Let the creative do the targeting.
  • Ad Set 2: Winning Interest Stack (Combine your best interests into one big audience).
  • Ad Set 3: Lookalike Stack (Combine your 1%, 3%, 5% lookalikes).
• Exclusions: ALWAYS exclude your purchasers (30 or 180 days). There is nothing more annoying than seeing an ad for a product you just bought.

2. The "Testing" Campaign (The Sandpit)

This is where you test new creatives and audiences without risking the performance of your main campaign.

• Campaign Type: ABO (Ad Set Budget Optimisation).
• Why ABO? You want to force spend on new things. If you put a new test ad inside your CBO Scaling campaign, Facebook might ignore it because it prefers the proven winners.
• Strategy: Create a new ad set for every new concept or audience you want to test. Give it a small daily budget. If it performs well after 3-4 days, move it to the Scaling campaign.

3. The "Retargeting" Campaign (Optional)

Unpopular opinion: You might not need a separate retargeting campaign. If you are using CBO and broad targeting, the platform will naturally retarget people who engaged but didn't buy. However, if you have a specific offer for fence-sitters (like a discount code), put it here.

If you're unsure about how budget fights between these stages, check out this breakdown on funnel stages fighting and budget allocation issues.

Scaling Without Breaking Things

One of the main fears people have is that if they change their structure, they'll ruin their current results. It’s a valid fear. But staying stagnant is worse.

When you scale, you shouldn't just pump money into the existing ad sets blindly. This is where the ultimate guide to scaling ad campaigns profitably comes in handy. You need to differentiate between Vertical Scaling (increasing budget on winners) and Horizontal Scaling (adding new audiences/creatives).

In the consolidated structure I detailed above, vertical scaling becomes much safer. Because your audiences are larger (broad or stacked interests), they don't saturate as quickly. You can bump the budget by 20% every few days without sending the CPA to the moon.

Common Mistakes to Avoid

Before you rush off to delete all your campaigns, here are a few things I'd warn you against:

• Over-segmenting by demographics: Don't create separate ad sets for "Men" and "Women" or "25-34" and "35-44" unless you have distinct products for them. Let the algorithm figure out who buys.
• Changing things too often: If you consolidate, give it time. The system needs a few days to recalibrate. Don't panic if day 1 looks a bit wobbly.
• Ignoring Creative Fatigue: Consolidation works great, but it burns through creative faster because you are spending more in fewer places. You need to be testing new ads constantly in your "Testing" campaign.

My Recommended Action Plan

I know this can be a lot to take in, especially if you're used to the old way of doing things. But if you want to fix your scaling issues and stop your campaigns from fighting each other, you need to simplify.

Here is the main advice I have for you:

Implementing this structure usually results in immediate stability improvements. You stop fighting the algorithm and start working with it. If you've tried this and are still seeing high costs, or if you're worried about making these changes on a live account that's spending significant money, it might be worth getting a second pair of eyes on it.

We offer a free consultation where we can look at your current setup and point out exactly where the inefficiencies are. No sales pitch, just a look under the hood to see if we can help you get unstuck.

Hope this helps!