Mid Lane

Annie is probably the simplest because she has point and click stuns and generous aoe hit boxes. Imho the ad melee assassins are the hardest to learn and master since not only are the high mobility dash moves and kit combos more difficult to use properly, the play style requires much more thought and precise execution.

Ahri is always a solid pick for any skill level. If you can land a straight line skill shot charm you can score kills easily and her ult can be both offensive and defensive to kill enemy adcs or get out of ganks.

Annie\Malzahar and Azir