If you have a Windows computer, then you could get Stopmotion pro or monkey jam, if you have a mac you could get iStopmotion. I use a DV camera, they arent to expensive I have a panasonic DV that works great. where are you from, if you can't get it near you, you can buy plasticine online, just so you are clear modeling clay is the same thing as plasticine, so if you see modeling clay that will work. You can always paint your own backgrounds, even if you aren't a good painter, splat some blue paint on a piece of wood, put some clouds and there you go, got yerself a background. For sets, I use a lot of model railroad scenery, it works great for that animation, but a lot of it can be expensive, if you are going to make trees just use real branches. Depending on the size you are working with, dollhouse stuff works good for props. I make a lot of my props too.
If you haven't seen the, here is the link to my animations, the Beaver Creek Episodes, http://www.youtube.com/view_play_list?p=A75AF9C769EA009D
if you have any questions on how to do stuff I would love to help.