You may want to learn every champion in the game and play something new every day because you can't resist the lure of the unknown and the exciting mystery of a new champion. But noooo that's wrong - people on forums and guides tell you that you have to play one role and one champion or you'll never be Challenger. I own 70 champions and I'm here to tell you that I think you should play whatever you want and tell the haters to shut it.
When I started playing League of Legends I loved when the next free week came along because it gave me the opportunity to try new champions. I would get so excited I would make a list of all the free champions and mark off the ones I hadn't played before and pick which ones I wanted to try out that week. Most newer players feel similarly as they don't know how all the champions work and it's great to try them out and get a feel for what you like. Even though I've tried almost all the champions at this point and the free weeks aren't as interesting to me, I still like playing a huge number of champions. I love the thrill and excitement of learning the skills and subtleties to a champion I don't know how to play.
Some say this play style makes it more difficult for me to win or improve because I don't practice the same champion or role. I disagree. Playing many champions gives me a much broader sense of the game, and an ability to be flexible with my role or champion for my team that can be very valuable. Most importantly, if I force myself to play the same champion over and over my heart just isn't in it. When my heart's not in it, I know I'll lose. I've tried to force myself to focus on one champion or role, but I find that it really stagnates me. My periods of greatest growth and improvement come from experimenting and trying new things. I'm not saying you should have a giant champion pool too. All I'm saying is trust your instincts and play what you feel is best for you and not what someone else tells you to.
Don't pick what championselect.net says is the best counter to your lane opponent. Don't pick what Insec is playing because he made a great play in the last tournament. Don't pick Blitzcrank just because he isn't banned this game. Pick a champion you actually want to play.