Strictly speaking lucky stones or gems if at all they are useful should be worn only after studying the horoscope in full and evaluating it and finding out which planets are malefics. An analogy would be if you have Vitamin A deficiency, you should only take Vitamin A tablets to offset the deficiency and taking multivitamin tablets will be counter productive in that the body will have to work harder for the excess vitamins to be thrown out of the body through our kidneys and make them work harder. Just by looking at Rasi or Star or Zodiacal sign and wearing Gems for that as you see in generalised predictions for Stars or Signs, to my mind is futile and could be even harmful to you.
Think about it, I for one will not suggest a Lucky stone looking at the rasi alone.