What Champion should I play?

So, I'm trying to figure out what champion I should play. I've been playing for two years, off and on, and I really wanna start understanding the game better. I've played mainly adc and some support, but I haven't been doing well for a while and I think my playing has gotten stale. I suck at anything close up, I just don't understand how to work those champs... But I'm a lot better with distance people (magic or basic attacks). I need to practice with everyone I've got to see what I'm doing well on and who I'm doing well with, but I'll go ahead and outline the ones that I'm working with:

(Free-to-Play) I like her tricks, but I have trouble with her r. I am not good with her hitting champs close up. I don't really understand her gameplay and don't really enjoy playing her. I would love to be better with Annie, but I stink. I don't do well judging her distances and often times get too close to the enemies. :( I love her, and I'm pretty good with her as long as I have a good support. She is a little squishy, though. (Free) I am pretty good with him, but I don't do well running toward people to hit them. I'm okay with her. I love the distance and really enjoy how she works, but I have a lot of trouble hitting anything with her. She's one I'll be practicing with, but I wish I could be more accurate. I'm moderate with Cass, but I have trouble with mana control. (Free) I've got trouble doing anything with his shooty attack other than running away. (Free) I did him once, and I was okay, but nothing special. I was supposed to be the adc but couldn't get enough kills, so my teammate ended up being the real carry. I only played him once in Howling Abyss though. (Free) I can't explain how many times I died playing as him. It was miserable. I have Janna, but I've got the same mana control problem. I can shoot pretty well, but sometimes I'll overthink and overshoot the enemy. :/ I'm a pretty good karma supp, but I've never tried her anywhere else. I want to, but I don't understand where I'd put her. I used to be descent at kat, but I've lost any skill I had with her. I have trouble gaging when a good time to go into the teamfight is but I love her power. She's insanely tricky but I want to master her. I don't know her playstyle really well though, and I have trouble figuring out when to b or fight. (Free) I found out that I am not a jungle player with him... Like at all. It was worse than Fizz. I'm okay with Lulu, but I think I've got the same trouble with all of my supports. I try to poke the enemy adc out but I end up getting my rear end handed back to me. I'm not sure what I'm doing wrong :/ I'm okay with her, but I can't land any of her q's :( I can work with her, but I have trouble with mana regen I'm semi-good with Teemo, I'd have to say this is the best champ I play, because he turns invisible and I can lay all kinds of traps. I do enjoy the traps.

If y'all have any idea of any champ that I might understand, please suggest. I appreciate it a lot! :)