People need to understand One For All isn't a very competitive game mode. It's mostly for fun. Most likely you are going to have some one on your team that sucks every game. Most of the time it won't be there fault because they are using an unfamiliar champ. Don't jump down there throats. Give them advice about the champ. Like how to build it and how to use it.
I played my first game trying the one for all and was out voted and stuck with 
. We were matched against 
. At first I was very annoyed that the majority picked a champ I had never played before. Then we started to lose and I became frustrated with my remedial Garen play. My teammates were very supportive and instructed me on how to build him and what abilities to max first. In the end I really enjoyed my self and spent a lot of the game laughing at my "special" Garen dying over and over again. The crazier thing that happened was that we ended up winning that game. Thanks entirely to the knowledgeable Garen players.
There's a very similar feel to ARAM in that you get champs that you don't know (or don't even own), and you just have fun with it.
I think there's a lot to learn with figuring out what you want to do. I was a support gangplank and I had to have better map awareness with a true global ult. The game before, I was Lux v. Heimer, and I had to learn how to lose lane, be patient under turret, and then have a good transition out of laning phase.
It is definitely not a mode for going in dead set on doing what you always do, and you have to keep in mind sometimes you're going to have champs you've literally never played outside of free week, and the guy across from you in lane mains his champ. Just stay cool.
