You seem to primarily like mid. In that case I have some suggestions for you to consider;
You have played many games on him and he's over all super easy and very OP in most team comps, especially after the CD on his E was buffed. Be mindful of assassins that out maneuver him at all stages of the game and learn to farm up your stacks and hit your stun.
Vs an AP heavy comp or any enemy that relies more on abilities than auto attacks, he's a monster. In general you can build mostly AP but throw in a Frozen Heart to even out your cooldowns and armor. This champ will teach you roaming akin to TF, and he's amazing in team fights and securing kills.
This is the tippy top of the AP assassins in the game. Learn when to use his E and you can cheese everything and take everything in turn.
You can play these champs into anything for the most part, but again, pick for the team comp and whichever is going to struggle the least vs the enemy comp.
In addition, learn when to roam, practice your map awareness, try not to die, and just over all remember the basics.