I can tell you what almost everyone on this forum will tell you: don't use any. If you really want to use it VERY SPARINGLY. Many a nice display (werm ) or an easy sybil. Too many flourishes weigh down your performance.
Keep it simple so that you don't drop cards and keep it traditional so that it accents your magic rather than stealing from it. Do card springs, card fans, and perhaps card twirls.
Some people might not class it as a flourish these days but boomerang card is one of the only flourishes that looks good on stage because everyone can see it clearly.