No harm in testing the waters in looking for a diamond. Although I think to do it properly you will need to wait and get the right diamond (wait until you've paid off your education, cars, and are financially stable, then find a really gorgeous rock).
You don't want to know how much I paid for my wife's diamond. That was way way too much than a practical person should ever spend on a single small purchase.
But hey, it makes the wife really happy, so it's worth it
PS. If I were you I'd choose a classic round brilliant cut stone, with a white gold (or platinum based upon your budget) band with baggettes (spelling?) on the side. Those are really popular, and are pretty timeless as well.
PPS. I can see you've spent some hard earned dough on your PC, which is definitely the right place to throw some cash!