Have fun before you try to get good. Think of levels 1-20 as something like childhood, a time for lollygagging and being a derp and learning everything you do learn accidentally.
Then you reach level 20-30, which is basically high school. You start setting up future success by buying runes, actually learning important stuff, and getting anxious for the subsequent ranked you will be doing eventually.
Then you reach level 30, which is like going to college. You learn more things than you ever have among people who seem to be the best people ever, and you finish up your rune pages to be a respectable ranked player who can fill any role.
And then you play ranked, which is like entering the real world. You realize everyone you met in college is fucking retarded and you've learned nothing of importance in your past 25 years, and now your shotcaller shithead of a top laner has went 0/9/0 and is blaming you for not camping their lane. All your hard work is for nothing, you got 1/9 in your placements and you're now stuck in a deadend league with no hope for promotion.
Welcome to the League of Legends.