Lots depends on what you want to spend....cro moly is a good, flexible material for road frames, alum is fast and responsive, but many times pretty hard on the "bod"...if you have a zillion dollars, carbon fiber is great!
You may want to try your bike shop for consignements before you spend the "big bucks" to see if you like it! also, EBAY is a good place to pick up an older bike. If you know what you're looking for you can save some "dealer" mark ups!
Get to a shop and see if you can get sized correctly on a fit kit, it'll save a lot of headaches! good luck!
sandy