this subject can get into a big discussion. mine are around 9 gpp. somewhere I read anywhere between 8 and 10 should be good. but part of the big discussion is how is the arrow flight at the weight you are shooting. it is pointed out that a 7 gpp arrow flying straight and true will out preform/penetrate a poor flying arrow at 10gpp. a good flying heavy arrow will fly flatter than a poor flying light one.
arrow weight is only part of the equation. this is why we go through the trouble of working on our form, release, brace height, etc. It all plays into the equation. once we find our 'magic setup', or our best setup, we take notes. then if we decide to experiment some more, we will have it wrote down what to go back to.
I, for one, have a tendency to experiment and try to improve. I have a plucking problem but it seems that is the one thing I work the least on.