League-of-legends – Which two roles are the best to master in order to carry a team and raise the Elo

In a game to game basis, there really isn't much you can do to get your team to buy wards other then just asking and hoping, but when you get to the higher elo games people take it seriously and will also be buying wards. In lower elo games/unranked people don't take it as seriously/have the same skill level as high elo games and either don't buy wards or take offence to someone calling them out on it, which just makes the team do worse. If you're the only one buying wards, just do your best to get wards around dragon (although this is less important in unranked/low elo play), baron, and your lane.

The best option is to go premade with people you know.

If you solo then yes you should ask people what builds are they using and what lanes they want to be in,people will often be ok and tell you how they plan to play the game,but of course there are times when you just get people that want to troll and there is nothing you can do about it.

Personally what i sometimes do when i enter solo queue is that i type in:"STOP DON'T LOCK IN" as soon as i enter queue,and people often listen and do not lock it after that,and then i tell them that we should build our team carefully and most people are ok with that. Of course some people get rude about it and lock in with random champion and there is nothing you can do about them,either dodge queue or stick with them and hope for the best.

I would also mention that even if you get really weird team combination that you can still win if you're lucky.Even if your team may have crappy combination there is a chance that enemy team doesn't have good combination either or that they don't know how to play their champions so good.So there is always hope.