Chinese is a funny language, I lived there myself and studied it for years using kids books and just speaking with the locals. Personally, while Chinese was my...5th or so language that I studied, it was somewhat easier because I was living in a small city in China where no one spoke English except for my students and few engineers that lived in the city.
Also, my friend learned it through Duolingo (or learned as much as you can with Duolingo), and is in Shanghai now, saying that it absolutely helped him.
With almost all languages, including Arabic, Hindi, and Chinese (some of the hardest languages to learn for native English speakers), the key is to find a community that speaks that language and immerse yourself with them. Right now I'm studying Spanish and I am only drinking Mexican beer, listing to the Spanish radio station to and from work, and eating at a Mexican restaurant while ordering for me and my family all in Spanish.