Many people will tell you that the most important things to consider when buying diamonds are the four C's: Colour, Cut, Clarity and Carat. Rubbish!!!!!!! All this information tells you is how much you have to compromise to meet your budget. Why can't you have the best?
If your a diamond boffin these are all important, if your a wearer of diamonds they're not.
What is important beyond them all is character. Many people buy diamonds on ebay comparing stones of similar size and grades and going for the cheapest, that is like comparing houses by design and specifications and ignoring location. Ask yourself why do I want a diamond?
The best diamond for you is the one that meets your character, so choose carefully, buy from someone who you trust, and always insist a decent picture if you can't view it first.
Most importantly, ask the seller if you can return it if you don't like it, the only thing worse than paying too much for something is buying something you don't like.