If you're on day 4 of a new campaign with 3 ad sets and all purchases are coming from just one, you're in a solid position to begin scaling cautiously. The best approach right now is to let it run for a few more days, ideally until day 5–7, to allow Meta’s algorithm to fully optimize and stabilize.
Once that happens, you can begin increasing the budget gradually by 20–30% every 3 days to avoid resetting the learning phase. If you're looking to scale faster, consider duplicating the winning ad set into a new campaign (or CBO) and testing a higher budget there while keeping the original running untouched.
As for the other two ad sets, don’t turn them off just yet—sometimes they just need a bit more time or creative variation to start converting. And yes, results often improve over time if you maintain consistency, avoid heavy edits, and feed the algorithm more conversions. Just be sure to keep an eye on creative fatigue and performance metrics as you scale.