How many days is the radio being flagged for low goodput? If it's a single day or a week out of the whole year, then it's not too bad. But if you're seeing low goodput all the time, then that's when you'll have to consider the next steps.
1. AP load (how many clients are typically on the AP when the radio is getting low goodput)
2. ARM (is ARM trying to make changes while my radios have low goodput)
3. AP location (is AP near interferences or high latency areas)
Usually, I start by looking at a VisualRF view (if AMON is enabled, can use Health overlay), and then drill down from there.