A/B testing is usually considered to be a best practice method, how to optimize existing campaigns (and not only PPC campaigns).
The basic idea is that you test two versions of a landing page / ad / user interface, etc. After your test collects enough data, you can determine with a statistical significance that one version performs better in CTR, conversion rate, etc. You can find many tools, if you want to perform A/B tests.
However, the problem is that it might take very long to perform these tests, if you have a low traffic on your website. On the other hand, A/B testing certainly is a valuable method for optimization.
Therefore, online marketing community have determined several best practices that are worth trying for A/B testing in low-traffic campaigns:
- Track Micro-Conversions, not Macro-Conversions
- Perform more tests at the same time (as long as they do not compete with each other)
- Test Radical Designs
- Use different approaches (qualitative, manual, etc.)
A/B testing with low traffic is not easy, but it is possible. You just need to try to be imaginative. However, you should never forget statistical significance!