If you are having some indecision on what to merit, check out the Dancer Merits thread. Some of the opinions are very biased and take a "my way or the highway" route, which is silly because no two dancers are alike. Other than a few of those this is the only way to go posts it offers a lot of insight.
Just keep in mind your specific playstyle. Do you prefer to solo, merit, endgame, DD, main-heal ect... Focus on what you enjoy the most. Remember the beauty of merits is they are not permanant, you can raise and lower them easily. Some of the merits lean toward agressive while others are more passive.