The following is a comment I added to a thread on this subject at the LingQ forum.
I have said before that I consider the word count to be a little like the mechanical rabbit that dogs chase at the dog races. Something to help keep you going.That said, the known word count represents your potential in the language. To realize that potential you have to put yourself in a situation where you have to use the language often. You will stumble at first, but the higher your language potential, or word count, the better you will do, and the sooner you will sense that you are fluent. The number of words needed to be comfortable will vary from language to language, since some languages are more inflected than others. 1000 words in English will equate to over 2000 in Russian or Korean , whereas other languages may fall somewhere in between. Based on English, 3,000 words gets you started talking to people, with lots of gaps. Once you are over 10,000 words you can engage people in more meaningful conversations and enjoy it. There will still be lots of gaps. It is a long road, and you will probably want to get over 15,000 or so to call yourself advanced. That is for English so you need to multiply by some factor for other languages. Remember, this is just your potential. You then need to get out and use the language a lot, and you will stumble around for a while trying to get your potential to turn in to real fluency. The choice of when to start engaging with people in the language will depend on your opportunities and personal preferences.