Data is data. Anytime you access the internet on your phone it's going to use your quota. Web browsing isn't terrible but any sort of media, including youtube and video chatting will suck that down.
You really need to decide if you want to really 'get off the internet' or not. You say you do but you keep asking about what stuff will really hit your quota. Just get a cheap DSL or cable connection and use the internet like a normal human being.