For Mehndi - I would go for a nice big jhoomer with earrings but if ur going to b wearing a jhoomer on the wedding day then mayb go for a matha pathi...just so you get different looks on each day...
I personally think when going for a mixed colour jewellry set for the wedding day, you need to take into consideration how it will come together with ur dress...so I think its safe to go with a one colour jewellry set, like gold or silver....but if you decide to go for mixed colour jewellry set, try to make it sure the colours are not so overpowering...if ya know what I mean..
Also, dnt stress..im sure you'll look amazing not matter what you decide to go with...