This is a common dilemma in Facebook Ads, and you're on the right track by thinking about testing creatives.
It's not ideal for continuous creative testing for the same audience within the same campaign, and here's why:
Audience Overlap & Self-Competition: When you create a new ad set with the exact same audience (Broad + Purchase exclusions) as an existing ad set within the same campaign, you create audience overlap. This means your ad sets will compete against each other in the ad auction for the same users.
Problem: This drives up your Cost Per Mille (CPM - cost per 1,000 impressions) and Cost Per Result (CPR), making your ads less efficient. You're essentially bidding against yourself.
Facebook's Algorithm: Facebook's algorithm is designed to find the best performing ad within an ad set and optimize budget towards it. When you have multiple ad sets targeting the same people, it confuses the algorithm and hinders its ability to learn and optimize efficiently across the campaign.
Learning Phase Issues: Each new ad set goes through a "learning phase." If you're constantly adding new ad sets, you might keep pushing your campaign back into this phase, preventing it from truly optimizing and stabilizing.
The Better Approach for Creative Testing:
Instead of creating new ad sets for new creatives with the same audience, you should generally do this:
Consolidate Creatives within ONE Ad Set: The most recommended approach for testing creatives against a single audience is to put all your creatives within one ad set.
Facebook's algorithm is smart enough to identify the best-performing creative within that single ad set and will automatically allocate more budget to it over time. This is how it's designed to work efficiently.
You can have many ads (e.g., 5-10+) inside a single ad set. The number depends on your budget and how quickly you want to get data. With $100/day, you can easily test 4-8 creatives effectively within one ad set.
Dynamic Creative (Optional but Powerful): For even more efficient creative testing, consider using Facebook's "Dynamic Creative" option at the ad level. You can upload multiple images, videos, headlines, primary texts, and calls-to-action, and Facebook will automatically combine them into thousands of variations and show the best-performing ones. This is excellent for rapid-fire testing.
So, revise your plan: Keep your current ad set, and add the 4 new creatives into that existing ad set. Pause the underperforming old creatives once the new ones have enough data to prove themselves.