Once you are lvl 30, you have a chance to play with everyone on league, this jump is really big and if you start playing ranked it will be extremely hard to play with these people. You will get a low rank and hate everyone. Try to get better slowly, get some runes and masteries going. And when you think you are ready, then play ranked games. I made this mistake myself and I regret it, it made me stop playing this game for 2 years or so.