Find some thing you absolutely love playing and are willing to learn. It is easier to lean if you are interested and happy because your brain engages the material more readily.
In season three I mained jungle and absolutely loved nunu jungle. I learned jungle route, the timing that most jungles were able to make their first clear on, the exact strength I needed to solo baron early, how to identify strong lanes that I should get fed so they would carry me, basically just learned a whole lot about the jungle. I also watched YouTube videos of nunu jungle and focused on what I could be doing better each game, learning how to invade more often and die less, and enjoyed it the whole time. I went from bronze to gold that season and absolutely crushed every game I got nunu jungle until I hit high silver low gold level.
Season 4 I didn't find any thing I really liked and tried to practice stuff but didn't just love anything and really want to practice so I didn't get any better and stayed silver all season. I burned out and took a while off after that.
I started this season so out of practice that I placed two accounts in bronze (second one is from leveling up with a friend who learned to play) and then fell in love with heimer and just played him a ton learning something every game. Getting good at auto attack harass, then better ward placement and awareness to avoid ganks since I'm always pushed top lane, then using my ult at level 6 to consistently dive and get a kill under tower while living. Also objective control is huge. Started playing heimer and nunu recently on the second account to rank it up fast and am like 20-2 in recent games because my heimer is so much better than it used to be, and I know how much damage I do for baron and dragon and have better vision control so we win with that a lot. Last game I played heimer bot lane (I won't adc bc I don't like it) and mid fed hard early but we won eventually in large part because we got 2 barons and something stupid like 7 dragons (50 minute game).