Diamonds are pieces of charcoal that look pretty. Let me be the first to introduce you to the wonder that is diamonique. Four out of five dentists can't tell that it is not real. Get it in a 6 prong solid platinum setting of course, not plated.
I'm joking of course, my wife would beat me if I bought her a fake diamond .. and yours probably will too..
I bought a real diamond that wasn't exactly cheap. You want to look at diamonds in a bunch of stores, unset, and learn about what makes them different. Personally, I'd rather one that has a nice cut and is nice size over a smaller one that you can't see any flaw in at less than 20X. Cut = sparkle, and even though they may be the same basic cut, there are huge differences in how they look because diamond cutters are different and work with different pieces of carbon.
Have fun shopping.....