How i level up fast

play the weekly gamemodes where the games end in 10 minutes and farm it

either get a boosting service or like @mdznf said, play ARAM

buy the exp booster for days and then play a lot, there's no shortcut
just keep grinding you will be level 30 before you know it

Play bot games and end quickly, the more you win the more exp you get

The new best thing she even g h the game were fun but it