Do you have any electrical or programming experience? What do you expect to do and how much do you want to spend? Is it for fun or do you want to accomplish something? Are you going to build your own parts or are you going to be stuck with store made parts? Do you know that some companies give samples or help people out? Do you know how much time you want to spend building or programming robotics? Are you a do it yourself kind of person or do you need a kit? I think you should answer these questions first.
You can literally spend thousands of dollars on Robotics. Some kits are over a thousand dollars.
There are different websites on Robotics that I could give you. They use different microcontrollers.
I'm not sure what is the best but if you want to use Arduino then you might want to check out the Roboduino. You might want to check Society of Robots, etc. Different companies have different forums.
I would recommend you don't jump in right away. I can give you a list of manufacturers or websites to preview and you can make your own decision.
They are great entertainment and personal enjoyment but unless they are used to help people, I don't find a need for them. I suppose people in school should be exposed to them and people should learn about them in case the chance arises that they might get to work with them one day but I can't tell the future.
What I suggest is you study prices around the web to see how much it is going to cost you.