[duo797]

That's kind of hard to answer. Maybe put more time into your vocabulary than you comparatively into your grammar? I tend to wish I had a greater vocabulary, but I'm certainly not sad that I studied grammar. You're going to have to get to both at one point or another, so I don't think it's really possible to say one is more "important" than the other. You could also try choosing the area that *you* feel you're weaker at at the moment. If you're feeling particularly confident about your grammar, spend a week or two working out vocab, and using it in patterns you already know. If you feel good about your vocab, try using it in some new grammar patterns.