K/D Ratio is how many kills you get on average in each life. You should be aiming for this to be above 1 - the higher the better.
G/C Ratio is how many times you grab the flag divided by the the times you capture it. If you almost always capture the flag once you've grabbed the flag, it should be close to 1, if you get killed or the round ends while you carry the flag, it will be higher.
