What mistakes did you make when you first started playing?
Title.
And by first starting playing, I don't mean "back when I was Bronze" or whatever. I mean what did you not know before you hit level 30.
For example:
When I first started I watched a lot of League youtubers so I didn't get THAT much wrong, but I used to think that red buff and blue buff were equal in strength to dragon. Also, whenever people said that you needed smite to get jungle items, I legit thought that it was part of a cross-promotion deal where you would get jungle items if you also had a Smite account.
on 
out of nothing.


that told me to stop chasing so far and play more conservative, even my actual brother who played the game for around a year at the time didn't help that much at the beginning.