First time, best time

I may be considered a relatively new player, as I'm playing LoL for over half a year or so. But, there's this one thing that I'm interested in. Thing is, I can't have my main champion. I pick one up, have a great game, or even bad, but I do get to the point when i realize I like the champion, and that I "feel" it. I play 30-40 games with it, and then, all of a sudden, I start to suck at it. And it's not that I'm in a stasis or something and just get better opponents while I'm just as good as I was, but no better. I can't figure out what causes it. I ALWAYS try to improve myself at this game.
Before I even downloaded the client I started to read game and champion guides and so far I didn't stop it. I make up my own builds very quickly, later finding out that the best guides here have similar, if not the same, runes, masteries, item choices, even the skill levelling order. I mean, there's this one champion that gives me creeps. [:Ahri:]. I just love her. So much I could play her all the…
Before I even downloaded the client I started to read game and champion guides and so far I didn't stop it. I make up my own builds very quickly, later finding out that the best guides here have similar, if not the same, runes, masteries, item choices, even the skill levelling order. I mean, there's this one champion that gives me creeps. [:Ahri:]. I just love her. So much I could play her all the…