There's no better way to ruin a perfect run than to have old shoes, blisters, or chafing. Here's some tips on running equipment:
Blisters and chafing can ruin a perfectly good run. Also, good running shoes are vital. I can't emphasize that enough. First, ban cotton. No cotton. Cotton chafes and soaks up sweat. It then clings to you and either makes you cold or hot, depending on the weather. A lot of running companies make "technical" clothing for running--lightweight synthetic fabrics that wick the sweat away and keep you dry and maintain a nice temperature. I didn't buy into it until I tried it. Now, I swear by it. There's comparison. In the summer, it's as if I'm encompassed in a cool breeze, and in the winter, it traps warm air and doesn't allow the sweat to cling to you and give you a chill. The same goes for socks--synthetic. I personally love the very thin, double, non-blister Wright socks. They're awesome.
Other pieces of equipment? You're running so you don't need much. But a hat and/or sunglasses for bright days is nice. And sunblock. For long runs, or if you sweat a lot, you can get a fuel belt--lightweight belts that are fitted with water bottles that make it easy to carry fluids for running. I love my fuel belt. I also love running to music so an MP3 player is a must for me.
Also, I have a heart-rate monitor I run with sometimes to make sure I stay in my target heart range. It mostly makes sure I don't go too high on my long, slow runs. It's also useful for making sure you're working hard enough. Most also come with a calorie calculator to track calories burned, which is handy. If you want to get really gadgeted up, you can include a pedometer to track your distance too. Some people even get a GPS to tell them where they are, map their route, how far they've gone, and their speed, but to me this is overboard; at least for where I am now.