Diamonds are a funny gem! I spend quite a time researching them before i bought my wife her engagement ring.

Besides Clarity the there is also Cut, Carat and Color those factors togheter make the price.

First of all YOU must like the stone, it has to sparkle and "spit out" colours (presume you want a clear diamond and not a yellow one)

There are sites online were you can type in the specifications of a diamond and you will get a market price, this might be usefull as a reference.

Be aware thought, nowadays diamonds can be relatively easily reproduced or enhanced.

Good luck with your hunt