To come up with a design- think about what you and the client consider bling- is it jewelry? Could it be crystals or will gold and silver dragees do the trick. Ask the client if they want an abstract cake- a novelty (high heel shoe- or a jewelry box) or a more traditional with flowers and ribbons etc- once you have an idea of what that is you will start to get a feel for where the bling should go-
If it will be a small cake- don’t over decorate- less could be more-
I always buy my black and red fondant and buttercream- it is just too hard for me to make and get right-