She is a much more difficult APC to learn when compared to Annie. Her Charm is VERY important to her assassination combo. I have trouble with it myself honestly.
And to quote others who have commented:
[{quoted}](name=Ale non è male,realm=EUW,application-id=3ErqAdtq,discussion-id=XrNBymR5,comment-id=0002,timestamp=2015-12-23T12:27:48.347+0000)
Try for various champs, and then play the ones you like the most
then the role you should play will automatically be clear to you once you will deepen the knowledge of your preferred champs
Every free champion rotation change take a look at the champions. Then follow their advice.
{quoted}
Find some champions you enjoy playing.
I personally lean towards tanks and fighters.
Some people lean towards mages, ADCs, and/or assassins.
It's up to your personal playstyle and preferences.
Basically: Find ones that seem like ones you might like and try them. If you don't like their playstyle, don't think about getting them and just try the next champion that interested you. Eventually you will find some that you like.