In your case, you're already able to express yourself and the grammar in your question and on your profile is good, so it's not really a question of what to do "first." I'd say you're on the right track already. Language is for communication, so one starts by learning the most common vocabulary first, and the most common structures for forming sentences. These structures are often referred to as "grammar," but that word tends to have negative associations for most people, due to bad experiences at school.