Travel Ideas?

I have been wanting to go on a trip to Europe or South America. Most likely I would like to go backpacking and spend my nights in a tent. This way I would save money and get to travel farther and see more for a lot cheaper. Problem is I do not know much about camping in either continent. Wondering if you can pretty much camp anywhere that is not very populated or if you need to pay for a campsite, how easy it is to find places to camp, and if you need to be 21 to rent a camp site. I was also thinking that I would blog about my travels. Just wondering how interested people would be in reading about my travels and if anyone has any tips or ideas for me.