It depends a lot on your running style and biomechanics. If you are lucky, you can get away with something pretty basic, but if you have any problems such as (like me) fallen arches or leg length discrepancies, you could cause yourself some problems. I've found it's best to go for something at least mid-price range, and look for last season's ones. Sportshoes.com often have shoes at 50% off, and the only difference to the full price ones is that they are a different colour.
It is definitly worth getting a gait analysis done to check for any potential issues, and most of all, build up your mileage gradually. Most injuries are caused by overuse, doing too much too soon, regardless of the price of your shoes!