Thought I'd share since I did quite a bit of research when I was shopping for an engagement ring.
Here are a couple of tips to get the most out of your money, especially if your future wife is not into "specs". Of the 4Cs, to stretch your dollar, focus on carat and cut, i.e. get the biggest diamond you can afford with the best cut. Size is important as it is the most obvious trait when someone looks at the diamond. No girl is going to appreciate it even if you tell her that it's flawless D diamond, if it's tiny.
As for cut, an excellent cut can make the diamond look "whiter" (as well as larger). It also brings the bling to the diamond. Very important so that your diamond does not look like a dead piece of ice. In my opinion, aim for a GIA 3X (i.e. triple excellent) diamond or an AGS 0 diamond, if it fits your budget.
Colour is less important because unless your diamond is more than a carat as it's unlikely that a girl will be able to tell the colour difference between, say an E and a G when comparing the diamonds face up, and encased in a ring. For best bang for buck, I would go for G or H, or even an I.
Clarity is where you can get the most value out of your purchase. Most people usually look at VVS / VS diamonds because the inclusions look bad on the cert, or they think that it is better to have a "clean" diamond. In my opinion, while that is fine, you won't be able to see the benefits of a high clarity diamond unless you are looking to get a >1.5 carat diamond or if you are always looking at it under the scope. So long as the diamond is "eye clean", i.e. unable to see any inclusions with a 20/20 vision 6 inches away from the diamond, it's good enough. Be wary though that certain clarity traits like "cloud" can make the diamond less sparkly, thus, choose carefully the type of inclusion. Also, traits such as blue luminescence can make the diamond look whiter, but at the same time, may result in a somewhat milky appearance.
Finally, although it's difficult to assess objectively because no two showrooms are the same, and each would be equipped with a dazzling array of light sources to make diamonds you see look as good as possible, trust your eyes! A good diamond will look great under any lighting condition. If a diamond looks "dead", just because it's not in a showroom, it's not the diamond you should go for.
By the way, here are a couple of photos of the diamond I got. Self taken under a scope. The diamond was purchased from a reputable online dealer.
Specs:- 1.05 ct, E, SI1, AGS 0 (Hearts and Arrows). By the way, hearts and arrows does not necessary mean that the diamond is shinier than one which is non H&A. If both diamonds have the same level of cut (e.g. GIA 3x), they should have similar light return characteristics.
Finally, as advised by others, get the best diamond you can afford without going overboard, or into debt. Diamond prices go up over time, thus, if you can afford it, better to buy now than wait till later.
