Many learners are told to focus on the 1,000 most common words and stop there. I've never done that. In Arabic I now have over 35,000 known words at LingQ, and while I can't use most of them yet, they let me follow podcasts on history and politics and discuss difficult subjects with my tutor. A big vocabulary is my potential in the language. Do you stick to common words, or do you push yourself to learn the rare ones?