@ Kash,
Yellow Sapphire is for Jupiter/Guru and Emerald is for Budha/Emerald.
The suggestion of the fingers and metals is perfect, your astrologer is not wrong on those counts.
The problem may occur because astrologically Budha and Guru are considered enemies so usually wearing these gems together is not advised, this is the general rule.
There may be a specific reason for him/her to advise both, it all depends on what/which problem you had approached your astrologer with.
I personally do not believe that you should not wear Yellow Sapphire and emerald together. If you do so, the desired results may get reduced or achieved a bit late or after some more problems, there may be some complications too, but if you remove the gem once your intention is achieved then you can avert complications.
Wishing you good luck, may God bless you and above all?????
Cheers