Purchasing a readymade product from a diamond retailer is a quick option, but you can make a sound purchase by choosing the custom-made route too. If you have ever gone to a diamond ring shop with your partner, you will often hear them voice out reservations about its size or setting. It would be better if you know this beforehand. This way, you can even buy loose diamonds and have them custom set as per her preferences.
Rather than having to mix and match, this lets you choose exactly what your girlfriend wants in the gemstone. If you already have a loose diamond that is cut into a standard shape, like an heirloom diamond, you can easily pick the right metal and setting for it with the help of a jewelry designer. Note that different precious metals complement different cuts of diamonds in different ways. For instance, the bright and whitish-silver colored platinum looks particularly good with princess cut diamonds.