Lynn, if you don't plan to camp often, get a cheapo and a couple of tarps and bungees just incase it rains. if you plan on doing more in the future, this is the one I bought and it's been through a acouple of very windy and and rainy weekeends and was totally dry.
http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=40000008000& productId=47612030&parent_category_rn=4500538&vcat =REI_SEARCH
the rainfly is nice because it allows air in and really secures down low to the ground. You can even seal out the wind gusts with an optional pole setup.