You are already doing some good things. Looking at guides, streams, and video's all help you get base knowledge on the champion. This is also much easier than playing the champion tons of times to discover their basic combo's yourself. Just make sure that whoever/whatever you are watching/reading, that these things are explained. You need to know why this champion does this or that or builds this or that. Don't just blindly follow guides or video's. Watching someone like Wingsofdeathx is a good example as he will explain lane match-ups, basic concepts, what he is doing, and why.
I would suggest going into a custom game or two and practice the combo's a few times. Don't do this so much that it is really boring, but you should start working on that muscle memory with no pressure. For example, can you instinctively do Jayce's all in combo from range? E, Q, W, R, W, Q, E? Or with brand how do you do the most AoE damage pre 6? Q, E (on the burning target to mark everyone with his passive), then W for the bonus damage on all burning targets. It isn't just knowing these combo's, but have you tried them each at least 5 times?
Once you actually know the combo's and have tried them a few times, even if just in once custom game, take it into normals. Nothing is really going to train you to play against people besides playing against people. Get into champ select, take your champion, and let people know that you are practicing that champion; trying to get better with them. If somebody responds like a jerk, just mute them at the start of the game. It isn't worth going through some random person's rage. You don't have to. Enjoying playing your champion can help growth so much, and ragers can inhibit that.
Also remember that most guides put forward one build to follow, but itemization, and even full builds can change depending on how the game is going and what your team needs from you. Enemy team full AD threats? You may want to consider tossing a Randuins or Frozen Heart into your build. Or both. Don't be afraid to try different items if the situation seems to fit, and if it doesn't work out realize whether it is not a good item (and why), if the itemization was wrong (bought too early/late), or if you were just too far behind for it to make a difference.
This is getting long but last thing. Record your games and watch replays if you really want to learn how the game went. You will see things in replays that you may have missed in game. It's amazing how much not having to actually worry about playing can clear your focus. I use na.op.gg's replay function. You can go to your current game and request a recording, then op.gg will record it (your pc does not have to spend the resources) and you can download the recording later. You don't have to install any 3rd party programs or anything, it just plays in leagues spectator mode so you can watch the entire game from any perspective.
Hope this was helpful. Good luck and have fun!
as they are usually high skill cap but rewarding for learning all the little tricks in their kit. However there lies the problem, I need to find a way to relearn all those little tips and tricks to these champions. I try to play them in normals but when I do, I'm always getting screamed at by other people for my mistakes and not in a constructive way either so I might be able to learn something. I've read the guides, I watched streams and videos on people who have played them before but when it comes down to actually practicing the champions I'm at a lose. I don't want to be a burden to those I get teamed up with but I really can't see a better way of learning the champion. Bots are too easy and I can't even think about taking it into ranked play so how do I learn? Am I over thinking this or is there something I've overlooked? Please help.
