Pre-compliance is not a smaller, cheaper version of the lab. It is a different discipline: you are not trying to prove the product passes — you are trying to prove that nothing surprising will happen when it does not.
Conducted emissions first
Conducted emissions catch most of the easy wins: power-input filtering, switching frequency placement, ground-return topology. Get this clean before you spend time in a chamber.
Then radiated, then immunity
Radiated emissions and immunity are where designs surprise you. Plan for short, focused chamber visits with a clear hypothesis each time, not a wide net.
Document every change
Every fix is evidence for the technical file. Capture before/after plots, the rationale, and the version of the design they apply to.