Hey BoilerMaker! Welcome to the Forum!
First place to start. Well you've already done that. You've got your budget. You already know your pocketbook limit and that will help the search fall into place.
Second. Well, you've done that too. You found Price Scope. Wow you're already off to a GREAT start!
The key to what makes a diamond look great is CUT. All the sparks and flashes of light and color that grab your eye.
Start by reading the Tutorial from the link on the Price Scope homepage. As you find areas you want more info on, try searching the forum threads by subject. Reading posts in the forum is a great way to help put some of the Tutorial info into perspective. Can't find info on the topic you're looking for? Just post your question on the forum.
Get out and cruise jewelry counters. Look at different styles of cut and settings. You will learn if you want a Round Brilliant diamond, or a Square Cut like a Princess, Emerald, or Radiant. You'll also get a feel for your metal preference, do you want a solitaire or a ring with side stone accents, and a rough estimate of how much the setting will cost.
Beware of Jewelry store lighting!!! While cruising and deciding on taste preferences, don't get carried away and buy anything. Just Look!!! Jewelry stores are notorious for "special" lighting to make crappy diamonds look great.
Once you've learned about CUT and the rest of the diamond C's and you've decided on the style of diamond you want, start playing with the search engine on the Price Scope homepage (left hand side). It has preset dimensions to pull up better quality cut diamonds. All you have to do is enter color, clarity, and carat weight preferences. If you decide you want the ultimate SUPER Ideal cut, use the upper right hand search engine.
One thing you may notice on the regular search results pages are several vendors listing the same diamond for sale. The vendors are using a diamond broker "multiple listing" of diamonds available that they do not physically have possession of. There are vendors on Price Scope who physically have the diamonds they offer for sale.
White Flash,
Good Old Gold, Nice Ice, and Superb Cert just to name the biggies.
If you ever have any questions, feel free to post on the forum. The only dumb questions are the ones that don't get asked, and there's always someone here willing to help.
Good Luck in your quest for your perfect e-ring!