Playing at level 18 sucks.
Teams of level 20+ players are stupidly hard to play against, because of tier three runes. It's like being 20 when all of your friends are hanging out at the bars. I've been on a crazy losing streak since hitting level 18, because now i'm up against more 20+ players than ever. I dislike being matched up with players who have a literal stat advantage straight off. Just because they're around my level doesn't make it an even match.
I don't know what to do about it. It's not fun at all.
and 
And look up some potions for season 6.
then full AP.