As the title says, I need help deciding who to main right now. I'm looking for a difficult champion that is really rewarding if you can play them right. I already play zed, but I don't like him enough to main him. Same with Ahri. My thoughts right now are 
Any other suggestions are welcome.
I can't decide that for you. That's something you have to figure out on your own. Of course, if you go by what other people or meta stats say, then you aren't actually maining anyone. You're just a tool doing what other people tell you to, and League is already bursting at the seams with those kind of people.
syn, ori, and tf.
Syn if you want to be able to destory your lane, push tower, and roam from there. TF if you want to tp to side lanes and get your team fed and make their lane easier Ori if you want full team fight control and lane zoning
and are the best two there and you should play them both since you wanna have a backup and they're both strong choices
has a strong laning phase, little to no counters, and is one of the best midlane teamfighters.
is good if u know how to attack people from behind walls and stuff, he's broken af if you get half decent with him.
does a bunch of damage, but that's pretty much it. Probably like the 2nd best midlane teamfighter because of his ult.
is really strong right now, so there's always her.
is considered op and nobody knows how to fight against her so there's her.
As for a really difficult champion that is very rewarding, it's probably The reason why orianna is so difficult is because she can not chase anyone at all and the ball's movement speed is kinda slow so there's that. Azir's hard cause you gotta keep track of like 1-2 soldiers and yourself while autoattacking and keeping people in your soldier range.
