First, when you wear 2 different metal accessories which have different tones, it will create an oddly colourful image of yours. Therefore, to be on the safe side, you should wear one colour from the metal of the accessories once at a time.
There are also several combinations which you could try to mix and match your jewellery to create more varied images. But remember that each combination should not contain more than 3 or 4 colours. One combination could be gold with brown or with royal blue and green. Silver is much easier to pair as it can go well it most of other tones of metal such as chrome, stainless steel and gold.
Secondly, when you choose to buy a piece of accessory which does not match your skin tone, it will either overpower your skin tone or will make it look worse. If you are not sure about which colour of accessories you want to choose for your skin tone, go with the classic colour blue or while and yellow metals. If you have rather pale skin, you could choose gold or platinum colours, which could enhance the complexion of your skin.
Overall, it is not that hard to wear jewellery in a correct way. All you need to keep in mind is keeping it simple, small and high class. You should also need to make sure you dress jewellery correctly for different occasions so that your jewellery would work in the way you intend it to do.
After all, jewellery is not a compulsory clothing item but if you want to stand out from the crowd, it could help you go a long way. Just make sure you wear it correctly and you will be surprised how classy and stylish you can be with pieces of jewellery.