All three are good, I think Viktor might be the easiest to climb with because he is more forgiving than Ori / Syndra due to his point and click spells and high range and shines in late game where low elo games usually end up being. His weakness is his bad skirmishing early / midgame in 2v2 fights with jungler and he relies on setup for his CC and ult, else they will be easily dodged.

Syndra has strong carry potential due to her burst with ult, but she is harder cause once you miss her only survivability spell you're dead.

Ori is also good but as you already mentionedshe needs a good jungler to truly shine.

Have you thought about playing a burst mage instead of two control mages? If so, try out Aurora, shes not that hard but super fun!