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I suggest you just play random champions once in bots, then continue to play them in normal in whatever way you want. You're low level, you don't have to be a meta slave yet. The main thing that's important now is getting you comfterable with a few champions, while learning what other champions can do against you to mess you up. It is for example important to know that the scorpion champ (Skarner) can you pull you back to his team with his ultimate or that a swirly white ring around the only child champion (Annie) means her next skill will stun you. Knowledge like that is priceless, so I suggest you mainly try to play 2vs2 lanes, as that's the easiest to identify range/cd/cost/what it does/additional effects of skills. Some easy champions to start you off are: Garen, Ashe, Annie, Jungle Amumu and Sona. Eventually you'll learn that each of these fits into a specific category of the meta. For any advanced knowhow like ideal skill set up, masteries, rune set up and build choices. Look up your champion at guide sites like Mobafire (more for beginners) and Solomid (more advanced). Runes get important when you're level 21+, for masteries try to sync roles/specific trees, like Annie's main role is to do damage, dive down the offensive tree with her, for item builds, just build the recommended items in the right top corner of the shop. Don't be afraid to ask your teammates for advice as some might be more knowledgeable on the game and 2 minds cacn think of more then one. If you have any minor questions you can post in the new players forum of the LoL site, where you'll usually get good anwsers or you can just post them here, I guess.

Also Corn, it does get annoying that you yell at everyone for their IGN, but do what you wanna do I guess.

It might just be coincidence, but I have never faced against a skarner once, not even on my own team. This is with random solo qeueus with level 12-17s and premades with 9 level 30s and myself at level 15. There's also plenty of champs I have not faced yet e.g. kog'maw, anivia, corki, irelia, etc...

In low level games you'll mostly see free champs only and some other common ones. For example, I usually see master yi, blitzcrank, jax, lux, kayle, teemo, tristana, varus, etc. While just learning game mechanics I think it's best to stick with 1 champ for a while, preferably AD carry, until you get the hang of things. After a couple of bot games, do real normal games against other low levels. Eventually branch out to other AD carrys and finally move out to other roles. The best thing though is to have at least 1 friend guiding you throughout the match, telling you what to buy, what to build, where to go, and basically what to do. You'll get the hang of things on your own eventually and you'll be able to figure out what to do when e.g. When to go on an enemy during a gank or focusing a 50% HP enemy early game with your partner.