At your level, you're looking for two things:
- New stuff (grammatical constructions you haven't encountered yet)
- Old mistakes (grammatical constructions you've learned incorrectly)
- Work through a frequency list of the top 1000 words in your target language with a tutor. Many of these words will be abstract function words, and the process of creating sentences with them will show you a lot of brand new grammatical constructions. Learn them using your flashcards.
- Read a book and note the times when the grammar surprises you. Learn those sentences with your flashcards, or take them to a tutor and create NEW sentences that use those same grammatical constructions.
- Ask your tutor to correct you every time you make a mistake when speaking. Write down what you should have said, and learn that sentence with your flashcards.
- Write! And get that writing corrected, via a tutor or via lang-8.com. Writing is ideal for finding holes and problems in existing grammar, and corrections are pretty ideal for fixing those issues. Turn all of those issues into flashcards.