Mr. Amit
Some astrologers suggest a gem stone considering the strength of the planet. Others will do as per the running period.
But as per KP system, we cast the chart as per the data, then decide which planet is connected to improving houses which are 1st, 2nd, 3rd, 6th, 10th and 11th houses. 1st indicates self efforts, 2nd indicates finance, 3rd house indicates valour, 6th house indicates success over opponents, 10th house indicates reputation and 11th house indicates fulfilment of desires or success in all undertakings.
As per the logic of Prof. K.S.K sir, if a drunken person is in the driver seat and he is energised with liquor, can the person take the passengers safely to their destination. Like wise if a planet is debilitated and is energised by wearing a gemstone, the evil effects would be more. So basing on the strength of the planets, which are connected to the improving houses, the gem stone pertaining to those planets will help the native.
Good Luck
JVS Rao (KP follower)