Still haven't quite found a champ I'm really wanting to get in a ton of reps with. Same old prob where I enjoy playing X champion a bit, but the get bored. I put the in reps, find out what I like/dislike, strength/weakness, matchups, positioning, etc, but I get bored after such repetition.
Most recently, I put in a bunch of reps on tf, donger, and kassadin. Dong has pretty close to the safest laning phase in the game. Eg its pretty freaking standard for to make my 1st back with > 1400 gold. But its also rare for me to pick someone off, so its a bit of a wash. His teamfight positioning is a bit of a challenge for me and it becomes insanely difficult to win if your team falls behind.
TF = lane phase isn't too bad except some matchups. Requires good use of ult/rotations and requires teammates capitalizing on good ults. Highly team dependent to get rolling at least.
Kassadin - I haven't played against any good mids yet when I've run him. He should have a weaker laning phase than some. I seem to do ok with farming. Also seems very heavily team reliant, but honestly, I've just been playing him with some lower elo, crazy time setups, so I can't really say. He does have a piss poor win rate at 46.39% out of mid, which makes me think the effort probably isn't worth it.
Another thing - so as I'm putzing around trying to figure out a mid I want to put in a bunch of time on, I'm looking at this chart:
http://champion.gg/statistics/#?sortBy=general.winPercent&order=descend&roleSort=Middle
I pay close attention to 3 things. 1 - win % 2 - play rate 3 - avg games. If the play rate is super low with a high win rate, I generally assume that's either very high elo folks or one trick wonders (generally the former). For instance, donger has a 55.64% win rate in mid with 1.08% pick rate. Avg games played = 195.19. So, its likely higher elo folks with much better mechanics than me that have put in ALOT of reps in w/ the champ.
For the currently kind of OP champs - lux is way at the top. 54.61% w/r, played 12% of the time, and most importantly, avg player games of 62.56. This means she's being played a bunch by folks that aren't exactly lux mains and they are still having a bunch of success. That means I have pretty decent odds of climbing in rank by playing lux (a champ I'm already pretty good at). Annie/Lux mid seem to be the current best mid picks for climbing based on stats and probable skill level required to do well.
Anyway, I start with that list and then think about who would be fun to play. Ahri's another one I could pick up and work on, but I actually kind of suck with her.