You cannot 'stack' GoF with another effect as they cancel each other out. For example, you cannot have a GoF dual axe and add that stone which has a chance to add 'quicken' to your attack. They simply cancel each other out. However you can add stones that add any Statistic like STR or DEX etc. Also you can add accuracy as someone mentioned (and as a bonus you actually get more than the stones say because its a % based, not value based increase) also you can add elemental damage stones too which are good for killing barbs. I guess it depends on what role you take in PK :3
EDIT: Not cancel out, just the added stone will not take effect