GIVE LOL A GO, YOU WON'T REGRET IT
Once you reach level 30 you will be able to play Ranked, where after completing 10 placement matches you will receive a rank between Bronze, the worst, and Challenger, the best. During your journey through the game you will discover there are not only numerous maps but also numerous gamemodes, each with uniques settings and playstyles allowing players to change up how they play and experience some variety from Norms, Ranked and Summoners Rift.
There are of course in game purchases that are available, but are not necessary. Masteries and is another part of LoL, which boosts your overall performance in games. You will receive one mastery point for every level you are. At level 30 you will have 30 mastery points and can use them to get certain stats, for example +30% attack speed. This can make the difference between a kill and a death. It is essential that you remember to use your mastery points wisely.
Though I think now is an appropriate time to mention some of the flaws of the game. Let's begin with the punishments that the game can give out. Previously, if you AFKed in a game you will be warned, then banned for a perod, but now you will have to wait a period of time, progressing getting longer, before you play a game. Another major problem is the amount time a game takes, ranging from 30 minutes to 2 hours! Overall I would certainly recommentd you give LoL a go. Though it does have some flaws, the positives far outweigh the flaws. Good Luck on the Rift Summoner. :)