If you are also new to cycling, and are a woman, I highly recommend the book "Every Woman's Guide to Cycling" by Selene Yeager. It is clear and concise and answered all my newbie questions and then some. I really liked the section on finding the right bike. This book helped me decide that what I really want and need is a road bike, not another hybrid (so difficult for this Sagittarius to commit, but that's another post). If you are really new, and not sure this is something you will stick with, I recommend testing several types of bikes then buying a used one. A good used bike will last a long time. My Trek hybrid is about 15 years old and still going! I got it off of craigslist for a few hundred bucks.
In my opinion, what you need to get started bike riding is simple and doesn't have to cost thousands:
1. a bike in good working condition-have it properly fitted at your local bike store...a poor fitting bike makes for a poor ride
2. a helmet!
3. a water bottle and holder
4. basic road safety...know how to signal, brake safely, pass, etc. Start out slow in a quiet parking lot to practice, if need be
5. cycling shorts or tights-these have the padding that makes riding so much more comfortable! If you don't want to invest now, you can really ride in anything...I rode in my yoga pants for months (make sure you secure any loose fabric!) until it became clear my rear would appreciate some extra padding.
6. lights -if you will be riding at dawn/dusk/dark
Numbers 1-4 are the bare minimum you need to get started. Once you get out there, use your gears to make it easier to go uphill (so many don't do this!?), keep a steady rhythm of pedaling (called "cadence"), drink enough fluid, eat some protein afterwards and enjoy! As you get more into cycling, you will probably want more appropriate gear (jersey, jacket that whicks away sweat, odometer to track your miles, gloves...and even...dare I say it? the shoes!).
I actually found myself at Sports Basement the other day buying a cycling magazine. It felt like I was buying porn. I felt the cashier knew I was a novice, and who did I think I was? LOL