I think staying in hostels would be a great way to travel on a budget. This will not only be easy on your pocket, you'll be able to visit more cities in a country at a time. Plus, you'll get to interact with people from different ethnicity, which is an experience in its own way.
There are many countries in central and southern America-Paraguay,Ecuador ,Nicaragua ,parts of Europe like czech , slovenia hungary and African countries like Malawi, Morocco with great wildlife and views which are not that expensive
You should Check out about Crowdsurfing it would save you a lot of money for you (Not recommended for large groups). It's a world travelers community. You can go to any country there will be kind people who would help out tourists.