1988 Toyota Camry Don't know what to do anymore.

So this all started with the engine not turning over. I charged it and it started right up. I replaced the battery with a used battery we tested to be good.
After that it started right up. A few days later, however, I am back to the problem of dim lights and not even a click from the starter. I charged the battery for several hours till the amperage on the charger drops to zero, indicating the battery should be fully charged. At this point, the dome light is still very dim and not even a click from the starter. I have tried everything I know and am now at a loss for ideas. Any suggestions?