What kind of jewellery do you already have? Is it one color only or do you like to mix yellow and rose gold?
I prefer YG because it looks best on my skin and because I think YG is so classic. I also have this thing about matching my jewelry to the hardware on my purses/shoes and since all of them are YG it was a no brainer for me.
RG is lovely but I don't like it with YG. It looks nice with WG however.