Getting back on from 2012ish

Just as the title suggests. I used to play this game like a fiend, but real life kicked me in the face and had to take time away from the game. For a bit of perspective, I started playing around the time Galio had just come out, and kept playing until around the time Darius and Draven were the most recent champions. Now I have my free time back, so I log in and... oh.. what? What are trinkets? All these items... and changes.. Oh god, and the Jungle! It's so full!

Needless to say, I was taken aback from all the additions so, I played the game the same way I used to. Same old builds and such. I didn't totally suck... but it was less than stellar. So all I ask of you all, is if it's possible to catch me up on some of the new gameplay elements that have been added. Perhaps explain some viable new strategies and advice on abandoning some old strategies that just stand up to the field anymore. Does Graves have a cigar yet? I've been watching some youtube videos to try to hopefully catch on to what's new, but it tends to not help since, I think most videos expect players to be up to date. Which is fine. Although I have to wonder the hell that brand new players must face, because when I started, it already seemed overwhelming to me.

Anyways... tangent over, all help is greatly appreciated, and I look forward to studying hard to get back into the league. Cheers!

tl;dr: Haven't played in years, what'd I miss?