Get the cheapest i3 laptop you can find. If you gave me more requirements, I'd give you more details. Chances are, 4GB of RAM will be plenty for you. If it isn't (only if you do HEAVY graphics/CAD work), 8GB of laptop RAM can be added cheaply later on.
If you're willing to wait a month or so, the new AMD CPUs and 2nd Generation i3 CPUs will be available. They're much better and in your price range.