Dont one trick, especially now. I have over 4k games on nothing but Jayce, and thats it. In the previous seasons I would agree for one tricking, but now, being a one trick is too risky. Riot isnt balancing the game for every champion to have the same carry potential. Honest truth is you need to pick 5 champions, and learn those 5 champions. Play 100 games of Jayce, 100 games of Shen, 100 games of Gragas, 100 games of Gnar, 100 games of Irelia, then 100 games of heimerdinger. The point of these 5 champions, is to pick entirely different type of playstyles so you have a clue for future metas. Jayce is good in early-mid game carrying metas, like Season 6/7. Shen is good in tank metas. Gragas is good in metas where team fights matters. Gnar is good against tanks. Irelia is good in snowball metas (current).
So pick the lane youre going to play, pick the 5 champions that have different meta playstyles, and play 100 games in a row on each champion. Then this way, when you go to play a different tank, youd have more of an idea on how to play them. Instead of picking 5 assassins that will for one only be good in burst metas, and you'll only know how to play like an assassin. Thats my honest advice to you.