I am pretty sure I went into my first UnTL'd visual novel with maybe 150 words.
Tip for those looking to start: Don't be dumb like me. It would be faster to just do the legwork than to sit there, looking up every single word. xD
Edit: Keep in mind I had a very good grasp on grammar going in, so don't think you can go in with just 150 words and eventually, someday come out and be fine, as I did.