The simple answer is you should see an improvement in the efficiency in your ad campaigns.
Although this can be difficult to measure precisely with certainty due to the sheer scale of Google’s Ad network, there are a couple data points you can look at
Your invalid traffic should decrease - Google Ads provides you with the current amount of "invalid" activity on your campaigns. You can view this data inside your Google Ads account (see screenshot below). Once Fraud Blocker is enabled, you should see the amount of invalid activity that Google detects to drop. HOWEVER, Google's size of their network is extremely large so as Fraud Blocker blocks bad traffic, Google often shifts your campaigns to new sources which can still produce invalid activity. So a drop in invalid activity isn't guaranteed.
Your conversion rates should improve - You should see improved conversion rates or sales ROIs on your ad spend.
You should receive less fake leads - If your campaigns focus on lead-generation, you’ve likely seen many fake leads come from your normal ad campaigns. These leads can often have repetitive or non-sensical names, unusually higher conversion rates, or simply be created in rapid fire (affiliate campaigns are notorious for this). So once enabling Fraud Blocker, you should see less spammy leads come through.
Less spikes in "irregular" activity - Marketers can often experience unusual spikes in web activity that may often occur in off-hours or be caused by DDOS attacks or bots. Fraud Blocker can help protect your ad campaigns from this activity since it blocks from bursts of fast, repetitive clicks that may occur.
More time on page - By blocking clicks from low quality users, such as from accidental clicks and bots, then the time on page should improve since you have more real shoppers visiting your site.
This isn't an exact science and these are just some of the indications you may see improved when using our service. If you have a higher amount of fraud in your campaigns then the improvements may be more noticeable.