Sorry if this sounds harsh, but stay the hell away from Cassiopeia and Azir. For real, they are two of the most difficult and complex champions in the game. I'd say most pros can't even play them at a high level. To borrow lastshadow's analogy, it's like you're playing pokemon, you just beat Brock and now you're trying to catch Mewtwo and fight the Elite Four. I was checking out your opgg, most of your other champion picks are similarly complex (Nami, Elise, Rengar, etc.). The champions that you have even win rates on are Sivir and WW, two simpler champions. I'd say this isn't a coincidence. Sure you might have a few good games on Cassiopeia or Nami, but what's going to gain you elo and ranks is consistency; what gets you better at the game is solid fundamentals. There's no point to spending all your energy wrestling with a difficult champion when there are so many other things in the game that demand your attention. Prioritize objectives, prioritize farm, learn when to trade and harass, learn how to mitigate your own mistakes and capitalize on your opponent's, etc. Watch videos on the game, you'll learn more than just grinding away at solo-q; here are two valuable resources:
https://www.youtube.com/channel/UCeGtVfZD9LVttCJzjIJLY1g
https://www.youtube.com/user/lastshadow9
I can understand if normals are boring for you; I also like ranked more since the games seem more competitive, but if you seriously want to start getting better at the game, you have to start taking it more seriously. I would recommend narrowing down your champion pool and roles, especially to easier champions. If you really want to learn Cassiopeia, fine, but recognize that you need to get your fundamentals and that it's going to be a hell of an uphill battle trying to learn those on Cassiopeia. Again, like trying to beat the Elite Four with a Mewtwo who won't listen to you at all since you only have one gym badge. Sure, Mewtwo is strong, Cassiopeia is strong, but so is like, Veigar (I've never seen a champion delete someone faster than a late game Veigar), and Veigar is a much easier champion to play.
One more thing to note; changing your champion pool won't make you better at the game, heck it might even make you a little worse while you're trying to learn your new champions; what it will do for you is allow you to get better at the game, more so than a complex champion would. These complicated champions are actually hurting your ability to learn and improve at the game.
Best of luck