Don't follow a strict build that has only one item build, one, strategy, and doesn't even bring up your opponents.
Rather than saying, "This item on this hero by this time..." realize that fighting different lineups requires using, and abusing, different tactics.
There are games where you would love to try that new non-conventional build on "whoever" but at the same time, you are going to judge the effectiveness of that build based on the percentage of the games you play successfully as that build. You lose your first game, you're at 0% win with that build, and you're going to think it's garbage, even if it is fantastic.
However, trying new builds is how strong builds, counters, and counters to those counters. It's also (usually) how the design new heroes, to counteract the current meta-game. Irelia for example.
So next time you read a cool build on mobafire, go try it out, but be sure to try it out in a successful environment. Don't try the latest AD Janna build when your team has no support, and you're up against Rammus and Shen. It's worth noting that building your hero to be automatically countered is less fun than trying that new build anyway.
...and stop being 'that guy' that locks in the new hero you want to try right away. Read, you know, MORE THAN ONE BUILD so as to make your next game enjoyable, regardless of what your 'nooby pubtrash feeder' teammates pick.
... also Lux is a good hero, but keep it on the down-low
This guide, along with the rest of mobafire, should keep your Normal games enjoyable.
tl;dr Extremely basic guide on countering