If you want just mess around with start with some free software www.blender.org has some free 3d software. Bryce is not free but fairly cheap ( www.daz3d.com ). Poser also is fairly cheap and you can get from Amazon. Those are mainly designed for stills but both do animation. For a more dedicated animation software you can try Swift 3d. ( www.erain.com ) that is about 250 dollars.
3d software is expensive. Very expensive. Trust me I know. Start out with the a few cheaper programs and see if you like it. The cheaper ones still can do some amazing things. 🙂
There is a ton of stuff out there so if you want to know more feel free to pm me. 🙂 I think it would be useful for you to first decide what sort of stuff you want to make. 🙂