A ground fault circuit interrupter (GFCI) or Residual Current Device (RCD) is a device that shuts off an electric power circuit when it detects that current is flowing along an unintended path, such as through water or a person. It does not protect you from an over current situation, that's what the breaker on the circuit you are on does. If your light fixture has ground issue, and I've seen lots of light fixtures that have ground issues that could be the reason the gfci pops. Have you tried the light on another circuit in your house that has a gfci circuit like a bathroom or kitchen? I have seen and had gfci outlets that are bad even new out of the box. If your not an electrican, hire one to make sure it is installed correctly. The gfci outlet should be the closest outlet to your circuit breaker. The idea is that when it pops it disconnects power from it and all the other outlets on the circuit.