Hi vikas2,
A gemstone used for astrological purpose should be a Jyotish gemstone. A Jyotish gemstone is a gemstone which does not have any flaws which are mentioned in our sacred texts on gemstones. A Jyotish gemstone should be untreated, unheated, natural, should have fine colour, cut, clarity, etc. If a natural gemstone satisfies all such conditions then only you may expect results.
Also consecration of a Jyotish gemstone and auspicious day and time of wearing a Jyotish gemstone plays an important role. These factors also impact on the effects delivered.
Is your Yellow Sapphire a Jyotish gemstone? A Natural Jyotish Yellow Sapphire is expensive. If the one you are wearing is not a Jyotish gemstone, then buy a Natural Jyotish Yellow Sapphire. If you cannot go for it, you may opt for its alternatives like Natural Jyotish Yellow Topaz or Natural Jyotish Heliodor.
Thank You.