Trinity One Trick?

Currently, Im in bronze 2 used to be bronze 1 but got demoted due to my little game knowledge at the the time. But let me get to the point. I'm having some troubles in choosing a champion to "main" but more specifically "onet trick" to use to climb rank. I've narrowed down my choices to three champions, Irelia, Akali or Riven. Could I get some help in deciding in which of these champs I should one trick. In terms of playstyle and difficulty, which one is more mechanically hard to play. Which is better rewarding if played right and correctly. And also in terms of which could most be beneficial to a bronze player if played correctly. Or if there are any better champs to so call main or "one trick". My main is currently jax with over 100 000 mastery points and level 7. The reason I want to move on from jax is hes quite simplstic and all and can'r really outplay insanely unless he's fed. So any tips on which champ???

Your help is greatly appreciated.

Ps. (looking for top lane champs)